Fire from First Principles: A Design Guide to International Building Fire Safety [4ed.] 0415832616, 9780415832618, 9781315852553, 1315852551, 9781317919032, 1317919033

Table of contents :
Content: Glossary of Fire Terms --
Theory --
Prevention --
Communication --
Escape --
Containment --
Extinguishment --
Assessment --
Information --
A Brief Overview of the Building Regulatory System in the United States --
Legislation, Codes of Practice and Standards in Hong Kong and Mainland China.

Citation preview

Fire from First Principles Fire safety is a fundamental requirement of any building, and is of concern to several professions which contribute to the construction process. Following on from the success of the previous three editions, Paul Stollard has returned to update and expand this classic accessible introduction to the theoretical basis of fire-safety engineering and risk assessment. Avoiding complex calculations and specifications, Fire from First Principles is written with architects, building control officers and other construction professionals without fire engineering backgrounds in mind. By tackling an overview of the factors which contribute to fire risk, and how building design can limit these, the reader will gain a fuller understanding of the science behind fire regulations, safe design, and construction solutions. All regulations content is fully updated, and has been expanded to cover the United States and China as well as the United Kingdom. The book is ideal for students of architecture and construction subjects, as well as practitioners from all built environment fields learning about fire safety for the first time. Paul Stollard is an architect and chartered fire engineer who has worked in this field for over 30 years. He is a former Director of Abrahams Stollard Ltd, and has been Chief Executive of the Scottish Buildings Standards Agency and Regional Director for Scotland and Northern England with the Health and Safety Executive. He received the ‘Peter Stone Award’, the highest individual award given annually by the Association of Building Engineers for his work on fire engineering and building standards.

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Fire from First Principles A design guide to international building fire safety Fourth edition

Paul Stollard with contributions from Brian J. Meacham, W.K. Chow and X. Dong

R

Routledge Taylor &. Francis Croup

LO N D O N A N D NEW YORK

First edition published 1991 Second edition published 1995 by E & FN Spon, an imprint of Chapman & Hall Third edition published 1999 by E & FN Spon, an imprint of Routledge This edition published 2014 by Routledge 2 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN and by Routledge 711 Third Avenue, New York, NY 10017 Routledge is an imprint of the Taylor & Francis Group, an informa business © 2014 selection and editorial material, Paul Stollard; individual chapters, the contributors The right of Paul Stollard to be identified as author of the editorial material, and of the individual authors as authors of their contributions, has been asserted in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record has been requested for this book ISBN13: 978–0–415–83261–8 (hbk) ISBN13: 978–0-415–83262–5 (pbk) ISBN13: 978–1–315–85255–3 (ebk) Typeset in Joanna and Univers by Swales & Willis Ltd, Exeter, Devon

Contents vii ix x xi

List of figures List of tables Preface Introduction 1 Theory 1.1 Fire science 1 1.2 Fire safety design

1 9

2 Prevention 2.1 Ignition prevention 18 2.2 Fuel limitation 25 2.3 Fire safety management

18

29

3 Communication 3.1 Detection 30 3.2 Comprehension/analysis 35 3.3 Alarm 38 3.4 Signs and fire notices 41

30

4 Escape 4.1 Occupancy 45 4.2 Travel distances 53 4.3 Rescue 60 4.4 Escape lighting 61

45

5 Containment 5.1 Passive measures: structural protection 64 5.2 Passive measures: compartmentation 72 5.3 Passive measures envelope protection 77 5.4 Active measures 79

62

6 Extinguishment 6.1 Manual fire-fighting 89 6.2 Auto-suppression 90 6.3 Fire service facilities and access

88

93

v

Contents

7 Assessment 7.1 Risks 99 7.2 Precautions 99 7.3 Balances and benchmarks 100 7.4 Simple generic fire assessment 101 7.5 Fire assessors 103 8 Information 8.1 England and Wales 108 8.2 Scotland 113 8.3 Northern Ireland 116 8.4 Other UK legislation 119 8.5 British Standards and International Standards 8.6 Guidance 128 8.7 Consultancy and advisory services 136

96

106

121

9 A brief overview of the building regulatory system in the United States BRIAN MEACHAM 9.1 Legal basis, roles, responsibilities and the structure of building regulation 139 9.2 Standards, product certification and evaluation 144 9.3 Building Code development processes 147 9.4 Structure of the International Building Code 150 9.5 Developments in support of performance-based building and fire regulations 153 9.6 Summary 156 References to Chapter 9 157 10 Legislation, codes of practice and standards in Hong Kong and mainland China W.K. CHOW AND X. DONG 10.1 Hong Kong 159 10.2 Codes in mainland China 165 10.3 Conclusion 170 References to Chapter 10 172

Glossary Index

vi

138

159

176 182

Figures 1.1 1.2 1.3 1.4 1.5 2.1 2.2 2.3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 4.1 4.2 4.3 4.4 4.5 4.6 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 5.14 5.15 5.16

Forms of heat transfer Standard compartment fire Standard fire growth curve Objectives, tactics, components hierarchy Matrix of tactics and objectives Human carelessness – skip fires Three lines of defence Building materials and fire growth Conventional fire alarm wiring Addressable fire alarm wiring Fire escape signs: safety colour green, shape rectangular Mandatory signs: safety colour blue, shape circular Hazard warning signs: safety colour yellow, shape triangular Prohibitory signs: safety colour red, shape circle with bar A fire safety notice: safety colour blue, shape rectangular A fire safety notice Stages of escape Inner room and access room Direct distance and travel distance One-way and two-way escape Egress versus refuge Horizontal escape to refuge Threats from heat and smoke Passive fire containment Collapse of upper storeys Stability, integrity and insulation Charring of wood Protecting steelwork Compartmentation of a building Compartments and sub-compartments Envelope protection Distance to boundary Pressurisation and ventilation Pressurisation Ventilation Smoke reservoirs Smoke curtains of different depths Use of upstands

3 4 5 10 11 22 24 26 36 37 41 42 42 43 43 44 54 55 56 58 59 59 63 64 67 68 69 70 73 75 77 78 80 81 82 83 83 84

vii

List of figures

5.17 5.18 5.19 6.1 6.2 7.1 9.1 9.2 9.3 9.4 10.1 10.2

viii

Mechanical and natural ventilation The neutral plane Sprinkler operation and smoke ventilation Fire service bridgeheads Access requirements for fire service vehicles Fire assessment Building regulatory structure Relationship between Model Codes, Reference Standards and other entities ICC performance Code for Buildings and Facilities Structure Maximum tolerable damage based on performance groups and design event magnitude Approval of fire safety provisions in Hong Kong The four fire code systems

85 86 87 93 95 98 140 144 155 155 161 171

Tables 1.1 1.2 1.3 2.1 4.1 4.2 4.3 4.4 5.1 5.2 5.3 6.1 9.1

Fire statistics, Great Britain 2011/12 3 Fire spread statistics, United Kingdom 1992 (percentages) 6 Injuries by source of ignition, Great Britain 2011/12 (percentages) 9 Sources of ignition statistics, Great Britain 2011/12 (percentages) 19 Building type and occupancy estimation 48 Building type and occupancy characteristics 52 Building type and travel distance 57 Minimum number of exits from large spaces 58 Building type and fuel load 66 Building type and structural fire resistance 66 Building type and compartment size 76 The suitability of extinguishing media for different fires 88 Comparison of International Code Council and NFPA Code development processes 151 10.1 Acceptance criteria specified in China 169

ix

Preface to the Fourth Edition The three previous editions of this book were written jointly with John Abrahams, who sadly died in 2001. He was one of the first practical fire engineers in the British Isles, working hard to improve fire safety in many building types, most especially health buildings. From our consultancy and teaching work in the 1980s, we had both come to realise that architects, and the statutory authorities, lacked a designbased guide to fire safety which would enable the underlying principles to be understood and incorporated at the earliest stages of an architectural project. Too many of the existing books simply expounded the legislation without real understanding, or over-complicated issues with too many detailed calculations. Therefore we wrote “Fire from First Principles” together. The first edition was published in 1991, and its preparation received financial support from “The Interbuild Fund”. It was such a success that subsequent editions appeared in 1995 and 1999. This new and completely updated edition is dedicated to John’s memory. Paul Stollard Edinburgh July 2013

x

Introduction Fire can be useful, but it can also be deadly. It has always fascinated and frightened; and as the proverb states; “fire is a good servant and a bad master”. Without fire, civilisation would be radically different, it might not even exist. However, the cost of fires which get out of control is high, and an average of seven to eight people die in fires in the United Kingdom every week. There is a risk of fire in every building that is designed, and it is accepted that complete safety fire is an impossible goal. The fire risks inherent in different building types are normally only highlighted when a particularly serious and fatal fire attracts public attention, such as the fire in January 2013 at the Kiss nightclub in Brazil which led to the deaths of at least 241 people. Such major fires underline the importance of building design and remind architects of their responsibility to minimise the risks of fire in buildings. However fire safety is not the only objective which an architect designing a new building has to fulfil. Aesthetic, functional, technological, economic, sustainability are also objectives which must also be satisfied, and there are many more. If the design is to be successful all these potentially conflicting objectives have to be integrated into a coherent whole during the design process. This is where the architect’s role is critical and the extent to which the integration is seamless is a measure of the expertise, and hopefully genius, of the architect. This book tries to help that process of integration by outlining the fundamental principles of fire safety so that architects, building surveyors and others in the design team can work from first principles to ensure an integrated design where safety is imperceptibly achieved without detriment to any of the other objectives. Where fire safety measures detract from the appearance, functionally or cost of a building then the architect has failed. Legislation attempts to set minimum standards of safety with which architects must comply; but attempts to comply without understanding the logic behind the law will lead to either inadequate levels of safety or cumbersome compromises. The design team should never treat legislation as design guidance. Legislation is written for enforcement authorities to check the designs being produced are intrinsically and fundamentally safe, not for architects to use as the basis of the fire safety design. Therefore this book does not start by describing the legislation, but instead works from first principles to establish a coherent understanding of building fire safety. The various tactics that the architect can use to ensure the safety of the occupants and the protection of the building are outlined as the basis for design. Working from first principles and considering fire safety throughout the design process, the architect will be able to achieve both safer buildings and ones

xi

Introduction

where the fire precautions are less intrusive. Fire safety measures will be less obvious and more effective if designed in, rather than bolted on afterwards. Although it is essential for architects to work from first principles, it is not necessary for them to become fire scientists. Therefore the principles are laid out as simply and clearly as possible; and to supplement these, a series of tables are included to offer approximate guidance on matters of fire escape and fire containment. These tables are intended particularly for student architects working at the sketch design stage, for whom it is far more important to gain a general idea of what is required, and why, than to understand the minutiae of codes and standards. The inclusion of these tables does not contradict the first principles approach of the book; rather they seek to provide rules-of-thumb which designers can use to check that they are heading in the right general direction. There is little value in confusing with unnecessary information, even less in presenting a spurious degree of accuracy through complex calculation. An architect should not need to get involved in anything which requires calculation: if the building warrants this, then a fire safety consultant should probably be involved. Therefore there are no calculations or formulae within this book. Similarly there are no references included in the first seven chapters, for this is not an engineering textbook, nor a treatise on fire science. Chapter 1 provides a brief introduction to the theory of fire safety and introduces the technical terms of fire science which the architect will come across from manufacturers and authorities. The main part of the book (Chapters 2–6) examines the fire tactics available to the architect to achieve fire safety: prevention, communication, escape, containment and extinguishment. These are considered as design parameters and are relevant throughout the design process. Consideration of these tactics will ensure that the building not only complies with the legislation, but more important, offers an acceptable level of safety. Chapter 7 considers the fire assessment of existing building, outlining the basic principles. Chapter 8 brings together all the information which an architect working in the United Kingdom might need including an annotated and structured bibliography in which further reading in specific areas is identified and a review of the current legislation in the various constituent jurisdictions showing how this relates to the principles of fire safety. Chapters 9 and 10 describe the fire safety legislative and engineering position in other major jurisdictions (the United States, Hong Kong and mainland China). These have been contributed by experts from those particular countries and each is well supported by references to the relevant documents and background texts. The book concludes with a glossary of fire terms. Although primarily intended for architects, this book can also serve as a useful basic text for the statutory authorities (fire service, building standards, health and safety etc). It is even more important that these groups can understand the first principles of fire on which the legislation is based if they are to be able to enforce it fairly and effectively. One of the common causes of problems

xii

Introduction

between the design team and the authorities is poor communications and a lack of mutual understanding. The early editions have already shown the value of a common textbook, working from first principles, in resolving some of the confusion and it has been used on many such courses.

xiii

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Chapter 1

Theory

Invariably there is too little time in the design process for architects to become fully involved in the technicalities of the combustion process and it just is not necessary. Architects do not normally want, and they do not need, to become fire scientists. However, to ensure an acceptable standard of fire safety without allowing it to dominate the design, it is necessary to be aware of what happens in a fire. Architects need to know what their design objectives ought to be, and how these can be achieved. Therefore this chapter briefly sketches in the few essentials that the designer should know, and places them in the context of the design process. It should not be necessary for architects to become involved in calculations, formulae and chemical symbols, and all of these have been avoided here. The references in the final chapters provide boundless technical data, but if architects become involved in the fine detail of chemical reactions or the structure of flames, then they have gone beyond the stage where specialist advice is essential. This chapter, then, is for the “ordinary” architect, who does not have the time or inclination to become a fire safety specialist. 1.1 Fire science This first section is intended to provide an outline of the key stages in ignition and fire growth and to outline the products of combustion. Some of the most common technical terms are explained, so that the designer will be able to follow manufactures’ literature and to discuss their designs with the legislative authorities. A full glossary of fire terms is included at the end of the book, as is an index. Terms in the glossary are highlighted in bold on their first use in the text. 1.1.1 Ignition Combustion is a series of very rapid chemical reactions between a fuel and oxygen (usually from the air), releasing heat and light. For combustion to occur, oxygen, heat and a fuel source must all be present and the removal of any one of these will terminate the reaction. These three ingredients of fire are so essential 1

Theory

that they are referred to as the triangle of fire. Removal of any of the three (heat, fuel or oxygen) will terminate the reaction and put out the fire. Flames are the visible manifestation of this reaction between a gaseous fuel and oxygen. If the fuel is already a gas and already mixed with oxygen, then this is described as a pre-mixed flame; if the fuel is a solid or liquid and the mixing occurs only during combustion as the fuel gives off flammable vapours, then the flames are described as diffusion flames. The gasification of a solid or liquid fuel occurs as it is heated and chemically degrades to produce flammable volatiles. Simply heating a suitable fuel does not necessarily lead to combustion, this only occurs when the vapours given off by the fuel ignite, or are ignited. The temperature to which a fuel has to be heated for the gases given off to flash when an ignition source is applied is known as the fuel’s flash point, while the temperature to which a fuel is heated for vapours given off by the fuel to sustain ignition is described as the fire point. If these vapours will ignite spontaneously without the application of an external flame, then it is said to have reached its spontaneous ignition temperature. Therefore it is not the fuel itself which burns, but the vapours given off as the fuel is heated. Once ignition has begun and the vapours are ignited, these flames will in turn further heat the fuel and increase the rate of production of flammable vapours. For the flames to exist at the surface of the fuel, the combustion process must be self-sustaining and capable of supplying the necessary energy to maintain the flow of flammable vapours from the fuel. In diffusion flames the rate of burning is determined by the rate of mixing of the fuel and oxygen and this is normally controlled by the degree of ventilation, the amount of fuel and the configuration of the room – all factors which the architect can influence. However, no such restrictions exist with pre-mixed flames and therefore the rate of burning can be very much faster. A common example of a pre-mixed flame is the laboratory Bunsen burner. A pre-mixture of fuel and oxygen in a confined space will lead to an explosion risk. Although a gaseous fuel can be mixed in different proportions with air, not all such mixtures are flammable, and it is possible to establish upper and lower limits of flammability outside of which flame cannot travel through the mixture. Throughout this section it is intended to refer to recent fire statistics, showing the practical applications in buildings of the theoretical issues of fire ignition, growth and products. In 20011/12 there were a total of 272,000 fires attended by public fire services in Great Britain; however less than 30 percent of these fires occurred in occupied buildings. In very general terms, these figures are very encouraging as they show the continuing downward trend in the number of fires and consequential injuries, which has been the case for a significant number of years. It is occupied buildings which are obviously of concern to the architect. In 2011/12 there were 312 fatalities in occupied buildings, with the number of other injuries over 10,000. It is important to distinguish between dwellings and other occupied buildings. Over 60 percent of fires in occupied buildings occurred in dwellings, but they accounted for around 90 percent of the deaths and non-fatal injuries (Table 1.1).

2

Fire science

Table 1.1 Fire statistics, Great Britain 2011/12

Fires Dwellings Non-dwellings All occupied buildings

44,000 27,000 71,000

Outdoor fires Chimneys Total

Fatal injuries

Non-fatal injuries

287 25 312

8,900 1,200 10,100

193,000 8,000 272,000

Source: Department for Communities and Local Government, Fire Statistics, Great Britain 2011 to 2012, derived from tables 1.1, 2.1 and section 3.1.

1.1.2 Fire growth The three basic mechanisms of heat transfer are conduction, convection and radiation; and all three are common in building fires. Conduction is the mode of heat transfer within solids, and although it occurs in liquids and gases, it is normally masked by convection. Convection involves the movement of the medium and therefore is restricted to liquids and gases. Radiation is a form of heat transfer which does require an intervening medium between the source and the receiver (Figure 1.1). Fires within enclosures behave differently and with different rates of burning from those in the open. It is important to understand the stages in the development of an enclosed fire as they will be the most common (Figure 1.2). The presence of a “ceiling” over the fire has the immediate effect of increasing

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the radiant heat returned to the fuel, and the presence of the walls will increase this effect, provided there is sufficient ventilation. With sufficient fuel and ventilation, an enclosed fire will pass through a series of stages after ignition: a period of growth, one of stability and then a period of cooling. The plotting of temperature against time from ignition will give a fire growth curve, and as these will vary to reflect the conditions of the fire, they are extremely useful to fire scientists considering the consequences of changing the conditions. The growth period lasts from the moment of ignition to the time when all combustibles materials within the enclosure are alight (Figure 1.3). At first, the vapours given off by the fuel will be burning near the surface from which they are generated; the ventilation is normally more than enough to supply oxygen for this, and the rate of burning is controlled by the surface area of the fuel. The duration of the growth period depends on many factors, but a critical moment is reached when the flames reach the ceiling. As they spread out under the ceiling, the surface area greatly increases. Consequently, the radiant heat transfer back to the surface of the fuel is dramatically increased. This will probably occur (in a domestic sized room with typical furnishings) when the temperature at the ceiling has reached approximately 550oC. The remaining combustible materials will now rapidly reach their fire points and ignite within 3–4 seconds. This sudden transition is known as flashover and represents the start of the stable phase of the fire. If there is inadequate ventilation available to the fire during the growth period, then the fire may fail to flashover due to oxygen starvation. The fire may

4

1.2 Standard compartment fire

Fire science

1.3 Standard fire growth curve

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die out completely, or it may continue to smoulder; and such a smouldering fire can be extremely hazardous as the enclosure fills with flammable vapours. If this is then mixed with a new supply of oxygen (e.g. by a door being opened), it may ignite with an eruption of flame, this effect being known as backdraught. This can be highly dangerous for firefighters attempting to enter rooms to search for survivors, and they have to ensure sealed or semi-sealed spaces are provided with some ventilation at high level before attempting entry. During the stable phase of an enclosed fire the flaming is no longer localised, but occurs throughout the enclosure. The volatiles are mixing with the incoming air, and the rate of burning will be determined by the level of ventilation and the amount of fuel present. It is this stage of the fire which is of the greatest significance to the architect because maximum temperatures will be attained. The fire resistance of the elements will have to take into account both the maximum temperatures which will be reached and the length of time for which they are likely to be sustained. The final cooling period sees the decay of the fire, once all available fuel has been consumed. Combustion can only occur if oxygen is present; many extinguishing agents operate by limiting the amount of oxygen available to the fire (e.g. carbon dioxide, foam, sand). The most common extinguishing agent, water, works by cooling the materials involved in the reaction. Without heat the reaction cannot start and if the materials are suddenly cooled the reaction will cease. The third method of extinguishing a fire is by interrupting the reaction itself, and dry powder does this by slowing down the reaction until it ceases to be self-sustaining. Looking at the statistics for fires in occupied buildings, it can be seen that between 33 and 43 percent are confined to the first material ignited and

5

Theory

only 9 to 13 percent extend beyond the room of origin, with the greater fire spread occurring in the occupied building other than dwellings. Over 90 percent of fires in dwellings do not extend beyond the room where they start. These figures are based on the spread of fire damage, and may not fully take account of smoke spread in advance of the fire (Table 1.2). The major products of combustion are heat, light and smoke. The smoke consists of chemicals produced by the oxidisation of the fuel. They are included with fine particles of burnt and unburnt fuel, drawn into (entrained in) a buoyant plume of heated air. Mixed with this there may be toxic gases produced by combustion. Light is unlikely to be a danger, but the other two products, heat and smoke, are both particularly dangerous and must be designed against. 1.1.3 Heat Smoke damage to a building can be severe, but it rarely causes total collapse; however, extreme heat can completely destroy a building. Steel will have lost two-thirds of its strength by the time it has been heated to around 600oC, a by no means uncommon temperature in a domestic fire. Concrete is a more resistant material; but as reinforced concrete depends on steel for its tensile strength, there needs to be sufficient insulation of the steel to prevent it reaching its critical temperature. Timber, of course, burns, but is a very good structural material as burning occurs at a fairly constant rate and so structural timbers can be oversized to provide a known measure of fire resistance. Bricks provide one of the best fire-resistant materials as they have already been kiln-fired at high temperature during manufacture. The design of structural elements to resist heat is the responsibility of the architect and will be considered in more detail in the discussion of containment (Chapter 5). The amount of heat produced in a fire is often regarded as a measure of the severity of the fire. An understanding of the factors which determine the level of heat production will enable an estimate to be made of the potential of the fire to destroy property, both where the fire started and in adjoining areas. In a compartment fire the rate of burning has been identified as being dependent upon the fuel and ventilation available. Therefore, it is these same factors which determine the heat which will be produced.

Table 1.2 Fire spread statistics, United Kingdom 1992 (percentages)

Confined to first material ignited Confined to room of origin Confined to building or origin Spread beyond building of origin

Percentages of fires in dwellings

Percentages of fires in other occupied buildings

43 48 8 1

33 54 8 5

Source: Home Office, Fire Statistics: United Kingdom, 1992 (1994), derived from table 56. (Note: this data is not included in the more recent statistics for Great Britain.)

6

Fire science

The quantity of potential fuel within the building is described as that building’s fuel load, and this will include both the fabric of the building and its contents. Estimating the fuel load can give guidance on the likely heat production and fire severity. The fuel load is difficult to establish accurately due to the multiplicity of materials likely to be involved. It is sufficient for the architect to be aware that the fuel load will vary depending upon the building contents and fabric, and that this should be borne in mind during the design process. The fuel load of, say, a large distributive warehouse is likely to be much higher than the fuel load of a sports centre of similar size (Table 5.1). When considering the potential for smoke production from the same materials, the term smoke load is normally used. It is not only the nature and amount of the fuel which will influence the heat output; the arrangement of the fuel is also significant. In essence the greater the surface areas of fuel exposed, the greater is the potential for rapid fire development. The proximity of the fuel to the walls and ceiling will also be a factor in determining the spread along those surfaces. The denser arrangement of the fuel, the longer the fire will take to build up to full heat output, and the longer it will last. The ventilation of the space where a fire starts will be critical in determining the fire severity and heat output. Both the air supply to the fire and the possible loss of heat by air removal are significant. The amount of ventilation will be determined by the shape and size of the window and other openings. When the windows are small, the size of the fire may be limited by the amount of oxygen which can be provided, a ventilation controlled fire. If the windows supply more oxygen than the fire needs, then the rate of burning will be controlled by fuel availability. Increasing the supply of the oxygen above that which can be used in the combustion process will serve to cool the fire as it becomes entrained into the rising smoke plume. Not only is the size of the window openings significant, their shape can also influence the fire severity. Experimental work has shown that a narrow, tall window will encourage a higher burning rate than a square window of the same area. The final factor which has an influence on the fire severity and rate of heat output is the size of the enclosure or room in which the fire is burning. While a larger area probably contains a greater fuel load, the distance from the fire to the ceiling and walls will slow down the fire in the initial stages. In general terms, the larger the area the longer the fire will take to develop, but the fire will be more severe once established. 1.1.4 Smoke A small percentage of fire victims die directly due to the heat generated in a fire or indirectly through the heat causing the collapse of the building, and this is a particular risk for firefighters and rescuers. However, the majority of fire deaths are due to smoke, either by the inhalation of toxic gases or to carbon monoxide poisoning. Various studies of fire deaths have found that over half of all deaths

7

Theory

were directly attributable to carbon monoxide poisoning. Very few victims are burnt to death, for although many may have “fatal” burns, almost all of these are received after death. The frequent burning or charring of bodies after death due to toxic gas or smoke inhalation can give a false impression of the relative dangers of different fire products. Smoke is the general term for the solid and gaseous products of the combustion in the rising plume of air. It contains both burnt and unburnt particles of the fuel along with gases given off by the chemical degradation of the fuel. The heating of the fuel and the emission of volatiles will cause a plume of heated gases to rise, and this will entrain air at its bases and as it rises. Some of this air provides the oxygen necessary to support combustion; the surplus will mix with the plume and become an inseparable element of the smoke. Although a complex phenomenon, smoke can be treated by architects as a single problem because they will be designing against the mixture rather than individual constituents. The architect must consider all smoke as dangerous and attempt to limit its production and control its movement. By far the largest of the constituents of smoke is the air that is entrained, and therefore in any attempt to estimate the rate of smoke production it is sufficient to assess the rate of air entrainment. This clearly depends on the size of the fire (in particular, its perimeter and the height of the rising smoke column) and the intensity of the fire (in particular, its heat output). In most buildings it is impossible to calculate accurately the rate of smoke production because of the large number of variables, and it is sufficient for the architect to realise that the larger the fire (and the larger its perimeter), then the greater the rate of smoke production. Sprinkler (more formally auto-suppression) systems are normally designed to limit a fire to a 9 m2 area (a roughly 12 m perimeter), and therefore in calculating smoke production from fires in sprinklered buildings, it is assumed that this represents the largest probable fire area, at least until the sprinklers fail. The appearance of smoke reflects its constituents and will vary from a very light colour to a deep sooty black. The density of smoke depends on the amount of unburnt particles carried up in the air, and the more dense the smoke is, the more dangerous it is because of the reduction in visibility. Visibility in smoke depends both on the smoke density and on the psychological condition of the observer. A very dilute smoke may only be an inconvenience, but when visibility is seriously curtailed, it can prevent escape and hence be extremely dangerous. Diluting smoke to keep escape routes open is almost impossible, so it is naturally better to prevent smoke entering in the first place. The architect must consider all smoke as potentially lethal, though the toxicity will vary depending on the nature of the fuel. All carbon-based materials will give off carbon dioxide and carbon monoxide. Even more toxic gases will result from some other fuels, and hydrogen chloride, hydrogen cyanide and the oxides of nitrogen are all common in fires. It is thought that combinations of these gases are even more toxic than when occurring individually due to the effect known as synergy, but the chemistry of such reactions is too complex

8

Fire safety design

and too little understood to be relevant to designers. It is more important for architects to be aware of the potential dangers of certain materials. Polyurethane foam, in particular, produces large amounts of hydrogen cyanide which is lethal in very small quantities. The 1979 fire at the Woolworth’s store in Manchester was a graphic example of the lethal nature of the smoke produced by burning polyurethane. Most of those who died were within a few metres of the escape stairs, but could not reach them because of the very rapid effect of the inhalation of the toxic smoke. Considering the injury statistics of fires, it can be seen that the pattern in dwellings is quite different from that in other building types. In dwellings around 85 percent of deaths and non-fatal injuries are the result of accidental fires, with the most common causes being smokers’ materials (32 percent of deaths and 10 percent of non-fatal injuries), cooking appliances (11 percent of deaths, 46 percent of non-fatal injuries), space heating appliances (8 percent of deaths and 4 percent of non-fatal injuries). In occupied buildings other than dwellings around 23 percent of deaths and non-fatal all injuries resulted from deliberate fires. While among accidental fires, the most likely to lead to injuries were smoking materials and electrical appliances. There were also a number of deaths and injuries attributable to “other sources,” mainly concerned with industrial or constructional processes (Table 1.3). 1.2 Fire safety design The previous sections have highlighted the dangers of fire in terms of the products of combustion, namely heat and smoke. The task of the architect in designing buildings which offer an acceptable level of fire safety is simply minimizing the risks from these products; fire safety design is all about protecting the building and its occupants from smoke and heat. Table 1.3 Injuries by source of ignition, Great Britain 2011/12 (percentages)

All accidental Smokers’ materials and cigarette lighters Cooking appliances Space heating appliances Electrical distribution Other electrical appliances Matches Others (including natural phenomena) Unknown Deliberate fire raising

Percentages of injuries in dwellings

Percentages of injuries in non-dwellings

fatal

non-fatal

fatal

non-fatal

84 32 11 8 5 7 2 8 11 16

86 10 46 4 4 9 1 10 2 13

76

78

24

22

Source: Department for Communities and Local Government, Fire Statistics, Great Britain 2011 to 2012, derived from tables 2.1, 2.10 and section 3.2, 3.4 and 3.5.

9

Theory

The measures taken by the architect to achieve these objectives can be considered as the components of fire safety design, and these are what is actually built or installed, the fire doors, sprinklers, escape stairs, etc. It is essential not to confuse such specific components with the more general tactics and the overall objectives. Fire doors are not an end in themselves they are just one component which will contribute to one tactic and so help to achieve the objectives. Similarly, compartmentation is a valuable tool for the designer, but used without understanding it may not assist (perhaps even hinder) the overall tactic and so not contribute to the objectives of fire safety. The hierarchy which needs to be understood by the designer is one of objectives, tactics and components (as set out in Figure 1.4) which collectively make up fire safety design. 1.2.1 Fire safety objectives The design process can be viewed by the architect as an attempt to satisfy a series of objectives: it is the search for a physical solution to a given set of problems. These objectives will include aesthetic, functional, technological, economic and sustainability issues. If a building is to be successful, then the objectives will need to be integrated into a coherent and balanced whole. Among the technological objectives will be those of fire safety. Fire safety is normally considered to consider both the safety of the people and of property in the building concerned and in the surrounding area. Therefore the fire safety objectives for the architect will be twofold: life safety and property protection. Other objectives might sometimes be relevant, but these will normally only be variation on life safety and property protection. For example, in the fire safety design of hospitals the maintenance of the service

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Fire safety design

is considered an objective (to avoid consequential life loss due to postponed operations and treatment), yet this is only a variation on life safety and property protection rather than a completely new objective. In designing to ensure life safety the architect is seeking to reduce to within acceptable limits the potential for injury or death to the occupants of the building and for others who may become involved. The objective of property protection is the reduction to acceptable limits of the potential for damage to the building fabric and contents. The architect will be seeking to ensure that as much as possible of the building can continue to function after a fire, and that the building can be repaired. The building should also remain safe for fire-fighting operations during the fire. The risk to adjoining properties will have to be considered, as well as the wider hazard of environmental pollution from the fire or even the fire fighting. The two principal products of combustion relate to these two objectives and, in crude terms, life safety can be seen as protecting people from smoke, while property protection concerns keeping heat away from the building. This gross oversimplification provides a succinct summary of the objectives which the architect must fulfil and the dangers they must design against. 1.2.2 Fire safety tactics There are five fire safety tactics available to the architect seeking to fulfil the objectives of life safety and property protection (Figure 1.5).

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11

Theory

1. 2. 3.

4. 5.

Prevention – ensuring that fires do not start by controlling and fuel sources. Communication – ensuring that if ignition occurs, the occupants are informed and any active fire safety systems are initiated. Escape – ensuring the occupants of the building and the surrounding areas can move to a place of safety before they are threatened by the smoke and heat. Containment – ensuring that the fire is contained to the smallest possible area limiting the amount of property likely to be damaged. Extinguishment – ensuring that the fire can be extinguished quickly and with minimal consequential damage to the old building.

Considering the five tactics in a logical sequence, the first is obviously prevention and only if this fails are the other tactics attempted. If the fire prevention is successful, the others need not be attempted; however as fire prevention will inevitably fail at some stage if the building is in use for long enough, provision must be made for the other tactics. Communication by itself, even if totally successful, cannot save lives or protect property, but its key role in ensuring fire safety means it must be considered as one of the five tactics and it sits at the centre of the matrix in Figure 1.5. If communication is successful, then escape, active containment and extinguishment can be attempted, but if it is unsuccessful then only passive containment remains. The success of escape will lead to life safety, its failure to death or injury. The success of extinguishment will lead to property protection and the limitation of damage, its failure to greater loss. The success of containment buys time for other tactics to be attempted; its failure leads to possible death, injury and greater damage. These five tactics provide the fundamental framework within which the architect should be working. A building designed with adequate consideration given to these five factors will offer an acceptable level of fire safety. Each of the tactics will be the subject of one of the next five chapters, with consideration of the implementation of the tactic through the design process from inception to completion. The relationship between these fundamental fire safety tactics and the current legislation which architects have to comply with is an interesting one, and will be considered under the section on acceptability and equivalency. This structure and the matrix were first published in the earliest edition of this book more than 20 years ago and it is interesting to see the extent to which they have been adopted in risk assessments, legislation and guidance (see Chapters 7 and 8). 1.2.3 Fire safety components The fire safety components are the weapons the designer can use tactically to achieve life safety and property protection. They are the building itself, its

12

Fire safety design

furniture, fittings and occupants. The number of components is limitless and depends solely on how they are categorised. It is not just the obvious (such as fire extinguishers) which must be included; everything from the wall coverings to the management practices may be relevant. Each of the components may contribute to one or more of the five tactics, and it is this complexity of interaction which necessitates a logical approach to the tactics of fire safety. There will also be interactions between the objectives, the tactics and between any of the individual components. For this reason measures taken to reduce the fire risk or hazard cannot be viewed in isolation, and the overall impact must be considered. For instance, the provision of sprinklers in a building to improve the property protection may reduce the risk of a fire growing beyond certain limits. This restriction in fire size and rate of subsequent fire growth should reduce the risk of structural failure and limit the amount of smoke produced. It should also increase the amount of time available for escape by containment of the fire. However, it will also probably reduce smoke temperature and this might increase the possibility of smoke logging. These problems of smoke control might result in an increased risk of life loss. There is also the risk that the sprinklers might not function properly and this might alter the risks to both life and property. The fire safety decisions are therefore complex ones, and the designer has to be aware that changing one component or altering the emphasis placed on one tactic can have an effect on the probability of success in each objective. In the more complex designs it might be necessary to attempt to consider such interactions quantitatively, but for the vast majority of projects it is sufficient for the designer just to be aware of the possible implications of his or her decisions. 1.2.4 Acceptability and equivalency Absolute safety from fire, where there is no risk whatsoever, is an ideal which it is impossible to achieve. The architect is never asked to provide such absolute safety, only to reduce the risks to property and people to a level which society regards as acceptable. The acceptable level of safety has traditionally been defined through legislation. However, legislation tends to be produced as a response to particular problems or fires and it rarely offers a balanced or reasoned structure for determining safety. There is an argument that the whole history of fire safety legislation is simply a catalogue of responses to serious fires. It can be shown that not only is legislation enacted in response to disaster, but also that changes in building forms and technologies occur. A very obvious example followed the Bradford City football ground fire in 1985, when the Home Secretary announced within two days that the higher safety standards of larger football grounds were also going to be required at third and fourth division grounds, yet this was the first fire at a football ground in which a member of the public had died (and none has died since). Public reaction to the perceived risk demanded such action

13

Theory

and also within the two days six other football clubs had either closed stands or started to remove perimeter fences and provide exit gates. Yet these reactions were not based on any rigorous assessment of risk and the legislation did not form any part of a general or comprehensive strategy for a common level of fire safety in all buildings. The vast majority of people who die in fires die in their own dwellings (Table 1.1), yet because these are small incidents which rarely gain media coverage the standards of fire safety required in domestic buildings are possibly lower than all other buildings. With much of the legislation related to fire safety being introduced responsively following particular tragedies, the existence of a coherent fire safety policy can be queried. Society is happy to accept as safe all buildings in which the dangers have not recently been exposed by a serious fire. Compliance with the regulations which are in force at one particular time is assumed to provide an acceptable level of fire safety, even though this level cannot be objectively quantified. There are alternative ways of measuring safety other than showing compliance with legislative standards. It is possible to design against specified risk criteria, for example designing to ensure that the probability is of a single death occurring once every thousand years and a multiple death once every million years. It is also possible to design against specified probabilistic or deterministic risk criteria (e.g. to ensure that people within a building are able to reach a place of safety in a time less than that for fire conditions within the building to become untenable). It is obvious that there is a point beyond which any increase in fire protection measures adds to the cost in undue proportion to the added safety provided. The fire safety designer must therefore achieve a balance between safety, economics and convenience. Acceptability must be discussed in view of the fact that absolute safety cannot be achieved and the law of diminishing returns, a cost safety benefit analysis. Another important concept, closely linked to acceptability is equivalency. Once architects are able to achieve an agreed level of safety by whatever combination of tactics and combination they choose, then the importance of ensuring equivalency is critical. Equivalency between two different fire safety designs means they achieve the same level of safety by different methods. This is sometimes described as a “trade-off”, the concept that one fire safety measure is being trade-off for another; for example does a concentration on fire escape enable the architect to pay less attention to fire extinguishments, or do measures installed to decrease the possibility of ignition balance a decrease in fire containment measures. Attempts to assess equivalency in terms of a single numerical value are difficult and can hide a number of contradictions. For example, one might regard the presence of sprinklers as providing an additional level of safety which would permit an increased escape distance. This would then perhaps reduce the annual loss of life with an occasional larger loss, resulting from the 1 to 2 percent of fires where the sprinklers fail to operate due to human or mechanical

14

Fire safety design

malfunction. A strategy for equivalence must recognise the distinction between average and societal risk. Calculations of equivalence are therefore neither simple nor easy to quantify; and for this reason, they are not normally explicitly incorporated in the legislative framework. The only one in common use in many national guidance documents is the relationship between increased compartment size where sprinklers are fitted in certain building types, as discussed in Chapter 5. Much of the current building legislation is couched in terms of what is “adequate” or “reasonable” however; these terms are not defined except by reference to guidance documents which set out performance or prescriptive standards for how different tactics or components must be designed. There is no attempt to define either acceptable safety or a system of determining equivalency, yet by saying that the guidance documents constitute what is “adequate” or “reasonable”, then any alternative fire safety strategy offering equivalent or better levels of safety should be welcomed. If designers are to be able to satisfy the objectives of fire safety without compromising other objectives (economics, aesthetics, functionality, sustainability), they need to be aware of the full range of different, but equivalent, fire safety strategies. 1.2.5 Traditional and fire engineering approaches to fire safety design The traditional fire safety design approach has been to identify certain fire safety components and then to set prescriptive specifications for them which have to be achieved. These often included: • • • • • • • • • • • • • •

travel distances and routes loadbearing elements of the structure roof construction separating walls compartment walls and compartment floors protected shafts concealed spaces and fire stopping internal surfaces stairways staff training fire service access manual fire fighting equipment detection and alarm systems emergency signs and lighting.

Such an incremental approach has already been criticised for limiting the design choice of architects, giving no guidance on acceptability and not helping in any calculation of equivalency. However, the most serious criticism of such an approach is the total neglect of some aspects of fire safety. Fire prevention is

15

Theory

hardly mentioned and smoke control rarely gets the attention that it deserves. The traditional approach was to regard all these components of fire safety as somehow independent and to demand a prescribed standard of provision in each of them. This limits the design flexibility of the architect and can lead to resentment of the legislation. Often the architect will start to seek loopholes or ways to get around the standards. Such an approach guarantees that designers and the statutory authorities will be in opposition to each other. The traditional approach also creates an artificial distinction between the requirements of the legislation which will concentrate on life safety and those of the building’s insurers which will be more concerned with property protection. Yet most fire safety measures will contribute to some degree to both life safety and property protection. The artificial separation of the two can lead to examples of both area of overlap and gaps. Conflict can even be generated by the differing priorities of the legislation and the insurers: in one major shopping centre in England the insurers offered a reduced premium if the mall was sprinklered, but due to the geometry this would have increased the life risk and had to be declined. The alternative approach to fire safety can be described as the fire engineering approach, and it is the one underlying this book. In this, the building is considered as a complex system with the fire safety design just one of the many interrelated subsystems. The architect is faced with designing not simply to satisfy a series of prescriptive standards, but to achieve an acceptable standard of fire safety. This will require an assessment of the equivalence of alternative fire safety strategies and the development of an integrated approach to fire safety. In the fire engineering approach, issues like fire prevention and fire communications can be given their due weight and the designer can fully exploit all the techniques of improving fire safety. The fire engineering approach demands an understanding by the designer of the fundamentals of fire safety, but it offers the opportunity to attempt unconventional ways of achieving compliance with the level of fire safety required by law. All that designers are required to do is prove that what they are offering represents a level of fire safety equivalent to what has been defined as the acceptable level. The fire engineering approach will begin with the recognition of the objectives of fire safety, life safety and property protection. Then the fire safety design must be prepared on the basis of an assessment of the risks and the ways these can be mitigated to an acceptable level. Chapter 7 considers the principles of risk assessment and Chapter 2 examines the specific ignition sources and fuel limitation. Chapters 3 to 6 cover the other four tactics and their potential for communications, escape, containment and extinguishment to balance the residual risks. Such an assessment of risks and precautions may be either quantitative or qualitative. Quantitative assessments are many and varied (e.g. fire growth modelling, smoke modelling, structural models, probabilistic analysis, structural response modelling, environmental testing and extrapolation of results, deterministic calculations, stochastic evaluation, fault tree, event tree and critical

16

Fire safety design

path analysis). Unfortunately, at present such methods are too complex in form and too limited in scope to be of significant value in most building projects. There have been steady improvements over the last 20 years, but there is still an absence of clear comprehensive models which bring together all the aspects of a fire safety design in an easily accessible and useable form which can be integrated into the design process. Therefore often the architects are reliant on qualitative techniques which rely on an expert-based assessment of risk. This book is structured around the fire engineering approach to fire safety and each of the following chapters addresses one of the five tactics available to the architect in preparing a fire safety design. Although, sadly, it is not yet possible to offer a simple quantitative system which would permit the full study of the equivalency of alternative proposals, an understanding of the fundaments will assist the architect in making informed judgements on equivalency and the acceptability of proposed fire safety measures. For architects and designers the hope must be that developments in fire science and engineering will steadily improve the legislation on buildings so that it becomes a coherent and comprehensive set of fire safety standards and enable the equivalency of alternative strategies for compliance to be easily assessed. Designers should be asked to achieve levels of safety defined in terms of risk to people and property, rather than in the prescriptive standards of compartment size, door widths or travel distances. Throughout this book, and in any approach to fire safety based on first principles, architects must consider fire safety in this manner.

17

Chapter 2

Prevention

The simplest and most effective tactic available to the architect to ensure fire safety is to prevent fires starting, namely fire prevention. If this tactic is successful, then there is no need even to attempt any other fire safety measures. There are two ways of preventing fires and they are related to the fundamental “triangle of fire”, outlined in Chapter 1. The three elements of the triangle are an ignition source, a fuel and a supply of oxygen, and as it is almost impossible, and most undesirable, to exclude oxygen from a habitable building, fire prevention has to concentrate on the other two elements. Ignition prevention and the limitation of the fuel available are the twin methods of fire prevention. There is also a minor role for the architect in ensuring that the plans for the fire safety management of the building are properly prepared, and this will be considered at the end of the chapter. 2.1 Ignition prevention In designing to reduce ignition the architect has to do two things: first to design out the predictable ignition hazards or sources; and secondly, to enable the building to be managed in such a way that the potential for ignition is eliminated. The actual design against the hazard and the design to permit management of the hazard must be seen together. The first necessity for the designer is an understanding of the most likely ignition hazards in the particular building type under consideration: it is essential to know your enemy if you are going to win. There are four basic classes of ignition: 1. 2. 3. 4.

natural phenomena (eg lightning) human carelessness (eg smoking materials, matches, cooking) technological failure (eg electrical wiring and appliance faults) deliberate fire-raising (eg vandalism, suicide, insurance fraud).

These four categories are not mutually exclusive and technological failure, in particular, is normally in part the result of human carelessness, technology alone 18

Ignition prevention

cannot be held to be the culprit when it is human misuse of that technology which has caused the problem. Considering the fire statistics on sources of ignition for occupied buildings in Great Britain, in 2011/12, a significant difference can be seen between dwellings and other buildings. In dwellings around 14 percent of fires were deliberate, and among those which were accidental the most common sources of ignition were cooking appliances (45 percent) and electrical appliances and wiring. In non-domestic buildings the percentage of deliberate fires was much higher at around 30 percent, and among accidental sources the most common were electrical appliances. There were also many “other” accidental sources in non-domestic buildings, reflecting the high number of fires caused by industrial or constructional processes. It has to be remembered that it is not just the number of fires which is significant, their severity is also most important. The figures on fire casualties given in Chapter 1 show that although certain sources of ignition may be very common, they do not lead to an equivalently high level of casualties. For example, cooking appliances account for a high proportion of fires in dwellings, but not nearly as many fatalities as smoking materials which only account for 6 percent of fires. This is probably because most cooking occurs when people are awake and able to react to a fire. Many smoking related fire deaths occur when a cigarette has been left to smoulder when someone has gone to bed causing a fire while people are sleeping. This just reinforces the importance of an understanding not only of what is most likely to cause a fire in the building type under consideration, but also which fires are likely to be the most dangerous (Table 2.1). 2.1.1 Natural phenomena The most serious natural ignition source is lightning, and the dangers of a lightning strike are well known; the 1984 fire at York Minister highlighted this in the

Table 2.1 Sources of ignition statistics, Great Britain 2011/12 (percentages)

All accidental Smokers’ materials and cigarette lighters Cooking appliances Space heating appliances Electrical distribution Other electrical appliances Others (including natural phenomena) Unknown Deliberate fire-raising

Percentages of fires in dwellings

Percentages of fires in non-dwellings

86 6 45 3 9 11 10 2 14

70

30

Source: Figure 2.1 and Department for Communities and Local Government, Fire Statistics, Great Britain 2011 to 2012, section 2.35.

19

Prevention

most dramatic manner. Earthquakes are also major fire risks through the damage they can cause to gas and electricity supplies, and fire is the consequent problem in earthquake areas. Forest fires are also an additional natural hazard for buildings adjoining or surrounded by large areas of woodland. In extreme situations, buildings may even be threatened by volcanic activity. However, in the United Kingdom the only major concern is lightning, and all architects should be aware of how to design against this hazard. The average lightning flash normally lasts for less than a thousandth of a second, but during this time a vast quantity of electrical energy is dissipated to the earth (perhaps a current of 10,000–100,000A and a voltage of many millions of volts). The lightning stroke may even be repeated over the same path two or three times within a couple of seconds. Lightning damages buildings as the current passes through building materials or along crevices between them, and energy is dissipated with the heat reacting to the water content of the materials to produce very hot gases. The buildings most at risk are those at high altitudes, on hilltops or hillsides, in isolated positions, and, of course, those with tall towers or chimneys. Designers must ensure that buildings at risk are provided with lightningconductor systems which will dissipate the shock directly to the ground. The finials of the lightning conductor need to be mounted on the highest point of the building and they have to be linked to the ground by a “down conductor”, normally of copper tape. This should be attached to the outside face of the building, and at ground level the down conductor needs to be linked to an earth termination (normally a copper rod drive some 3m into the ground, or a copper plate buried below the surface). Experience shows that a lightning conductor on a tall building will protect everything within a cone extending around the building for a distance equivalent to the height of the conductor finials (sometimes described as a “bell tent protection”). Buildings or parts of buildings, outside or reaching above this cone will need their own protection. It has to be stressed that lightning is one of the most complex of natural phenomena and some of its manifestations are still far from fully understood. It is tragic that it was York Minster which suffered so badly in 1984, when, at the time, it had one of the best lightning protection systems of any cathedral in England. 2.1.2 Human carelessness Probably the most common cause of ignition, and certainly the hardest to design against, is human carelessness. Almost all fires started by smoking materials or matches could be avoided, yet these are one of the major causes of domestic fires and consequent loss of life. Similarly, the continuing high incidence of fires concerned with cookers and stoves are normally due to human carelessness. Issues of public education and the encouragement of safety in the home are beyond the remit of this book, but there are some contributions the designer can make – the simplest, on electric cookers, being not to site the master switch behind the

20

Ignition prevention

cooker, but to one side and in an accessible position. Changing social attitudes and behaviour can make a huge difference and in the last 20 years the decline in the making of chips in deep fat fryers in the home has definitely led to a reduction in deaths and injuries. In non-domestic buildings there is even more the architect can do in, most significantly, the provision of adequate storage space. Insufficient badly sited storage will inevitably mean that the workers within a building will start to store goods in corridors, kitchens or wherever it is easiest for them. This may well bring potential fuel into proximity with potential ignition sources and in addition might block circulation spaces that will be needed for fire escape. For example, in hospitals it is highly dangerous if staff start to store flammable materials (such as linen or disposable bedpans) in areas with an ignition hazard (such as kitchens or treatment rooms). In many developed countries there are now restrictions on smoking in public buildings with staff required to go outside to smoking shelters or just the street. This obviously reduces the risk of ignition, unless there is a culture of illicit smoking within the building with staff finding unfrequented and hidden areas in which to smoke surreptitiously. This used to be a serious problem in storage and distribution buildings. Smoking remains a major ignition source in domestic buildings, but here there is little opportunity for the designer to play any role in reducing the risk. It is essential that in designing the layout of the building the architect has an awareness of how it will be used in practice and at least makes a guess at how it will be misused. Areas with a high ignition hazard (e.g. kitchens) should be placed as far as convenient from areas with a high life or property risk (e.g. bedrooms or special store rooms). This simple method of ignition prevention can similarly be applied to domestic buildings where the biggest ignition risks are the kitchen and the living room (probably highest smoking risk), while the biggest life risks are the bedrooms. The architect should ensure that the escape routes from the bedrooms are not jeopardised by passing through the living or kitchen areas. The siting of rubbish areas and skips is equally important as they are very common sources of ignition (Figure 2.1). 2.1.3 Technological failure Ignitions resulting from technological failure are even more the responsibility of the designer and need to be consciously considered during the planning process. Just as perfect fire safety is unobtainable, so it is inevitable that all building services and systems will fail. The architect must ensure that such failure is predictable, controllable and repairable. In the layout of the building the architect must be aware of the areas which pose the greatest hazard in the event of technological failure and design to minimise the consequences that would result from such ignition. Areas such as plant-rooms, laboratories, boiler-houses and large kitchens need to be sited where their threat is minimised. The separation within a building of those areas

21

Prevention

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where there is an increased threat, and those areas where there is an increased risk to life or property, is important. For example, in a large factory the paint spray shop would be kept at some distance from the main stores, and in a shopping centre the children’s play areas should be distant from the rubbish and plant areas. The services within a building, notably the electrical installation, will always be a major ignition hazard, and the architect must tackle this in both the short and the long-term life of the building. In the short term, it must be ensured that the services and installations are correctly designed, specified, constructed, checked and commissioned. In the long term, provision has to be made to permit checking and replacement of the installations, so that these functions are easily carried out and there are no problems to discourage regular maintenance. The maintenance manual for the building is a crucial fire safety document specifying precisely what is necessary to ensure that all services are maintained to the necessary standards. It is in the architects’ own interests to see that it is as comprehensive as possible, as it will relieve them of some of the liability for the building, transferring it to the building’s owners and occupants. The maintenance manual should cover all services (electricity, gas, communications, water, etc), the lifts and the building’s active fire safety systems (alarms, detection, smoke control, sprinklers etc). The maintenance manual is also a sensible place to record particular materials or building elements which require special attention because of their role in the fire safety of the building. It may be that fire-retarding materials have been used, but that these may not be immediately obvious to the occupiers (eg fire resistant glass, intumescent coating or fire retardant paints). Such materials will require particular care and should not, of course, be repaired or replaced by materials which lack these characteristics.

22

Ignition prevention

2.1.4 Deliberate fire-raising It is often very difficult to prove to the satisfaction of a court of law that a fire was deliberately started, and many fires which probably were deliberate do not appear as such in the statistics. There are five main categories of deliberate fires, some easier to design against than others. They may be started for financial gain or to conceal a crime, or as malicious vandalism, casual vandalism or as terrorist acts. Fires for financial gain include those lit by the owners or occupiers, the classic insurance frauds, or attempts to resolve a company’s financial problems by destroying plant or buildings. Alternatively, the fire may be started by an outsider or competitor who stands to gain from the destruction of the buildings or company. As such fires are likely to be carefully planned, it is almost impossible for the architect to design against them; anyone who is determined to burn down a building will eventually succeed, especially if they already have an intimate knowledge of the layout and construction. Fire-raisers are likely to want to conceal their crime as an accident, therefore the only defence the architect can offer is to eliminate the opportunities for accidental fires (as in the previous section). Again, there is little the architect can do in the design to prevent fires which are stated to conceal a crime. Someone who wishes to hide the traces of a murder or burglary by burning down the building will not be deterred. However, it is most likely he or she will be caught as unplanned fires very rarely succeed in destroying the evidence. Unfortunately, fires started by acts of malicious vandalism are not uncommon and the classic example is of groups or individuals who attempt to gain revenge by starting fires, perhaps the dismissed worker who, rightly or wrongly, has a grievance against an employer and decides to take revenge. As with fires ignited for financial gain, it is probable that such a fire-raiser will have a good knowledge of the building and the working practices, so there is little the designer can do to prevent such fires. The statistics show that a significant number of fires in Great Britain which appear to have been ignited as a result of casual vandalism have grown to cause major damage. These are distinct from acts of malicious vandalism, because there is less intent to destroy and less planning of the fire. This is particularly true of school fires, which in some cases have led to the destruction of the entire school. The architect can do much to reduce the risk of such fires by controlling access to the building or to particular areas of the building. There are three lines of defence (Figure 2.2) around a building: first, the perimeter of the site; second, the building face; and third, the divisions between different parts of the building. Obviously the amount of damage a fire causes will increase as each of these lines of defence is breached. At the first line of defence, it is desirable to have some form of hedge, fence or barrier, and permitted entrances should be marked by at least symbolic gateways. Good lighting can also play an important role in reducing the risk of unauthorised access.

23

Prevention

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At the building face the architect wants to control the number of entrances and ensure that the grounds of the building are protected by passive surveillance. Such surveillance does not necessitate continuous observation; rather it should convey to intruders the feeling that they are indeed being observed. Obviously particular fire risks should not be left exposed at the building face, whether these are rubbish areas or simple store rooms. The massive fire at the Summerland complex on the Isle of Man in 1973 was caused by young boys smoking in a small shed, which when it accidentally ignited collapsed against the outer face of the leisure centre, in turn ignited this, spread rapidly because of the use of Oroglass, and eventually caused 50 deaths. The third line of defence is within the building, and here the consideration of circulation routes is very important. Normally non-staff circulation should be kept to a minimum, and where large public spaces are inevitable the circulation should be planned to provide passive surveillance. Closed-circuit television (CCTV) offers a more expensive means of extending the surveillance system and, again, it is not always necessary to have someone always monitoring the system for it to provide an effective deterrent. The final category of deliberate ignition is terrorist attack and here it is possible to identify which buildings are most likely to become targets. However, not only are government and military buildings attacked, recent campaigns by groups protesting on environmental issues or animal rights, have spread the range of targets to retail outlets and university buildings. An architect involved on a sensitive building should seek to protect against both incendiary attack and the risk of fire consequent upon the detonation of high explosives. While the technical details of anti-explosive design are beyond the scope of this book, the

24

Fuel limitation

greater impact the architect can have is in the control of access to the building. The decision to include underground car parking is an example of a bad design decision which led to costly additional anti-terrorist measures at the Scottish Parliament, especially after the Westminster parliament had already experienced a fatal car bomb in such a location. 2.2 Fuel limitation Fuel limitation, like ignition prevention, is determined by the success both of design and management measures. It is most definitely an area where the architect can play a significant role: though unless the building is managed and used as intended by the briefing and design teams, it will be impossible for fire prevention measures to work most efficiently. It is hard to separate design from management and, for this reason, they will be considered together. Limitation of the amount of fuel available will help reduce the dangers of fire in two ways. First, by controlling the amount of material which will be able to burn and release heat to feed the growth of the fire. This is described as the fire load of the fuel. Second, it will control the amount of smoke which can be produced. The amount of potential fuel which will burn to produce smoke is often described as the smoke load, and this may be different from the fuel load, depending on the smoke generating characteristics of the material involved. It is possible for a fuel to have a low smoke load and a high fire load, or vice versa. Two types of potential fuel are specified by the architect: the building fabric and the building’s contents. 2.2.1 Building fabric One of the problems for the architect is the plethora of terms used to describe the fire safety of materials. Unfortunately, it is not always possible to define a material as simply safe or unsafe, for it is necessary to know a little more about the conditions under which it is safe. Architects have to be wary of manufacturers who simply assure them that a material has a fire certificate, it is essential to know what the certificate is for and what that actually means. The confusion which can result from the failure to comprehend the differences in fire safety terms can be clearly seen in such terms as “ignitability” and “fire propagation”: although materials might be treated to make them hard to ignite from a small source (ignitability), such treatments may not affect their rate of burning (fire propagation) once ignited. The essential characteristics of building materials which can be measured (Figure 2.3) and which the architect should be aware of are: 1. 2.

Ignitability – the ease with which a material can be ignited when subjected to a flame. Combustibility – whether or not a material will burn when subjected to heat from an already existing fire.

25

Prevention

2.3 Building materials and fire growth

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There are tests and standards for each of these properties, and these are outlined in Chapter 8. The first property, ignitability, most definitely concerns ignition prevention. The next three (combustibility, fire propagation and surface spread of flame) are concerned with fuel limitation as they will determine how fast a fire will spread in the early stages of fire growth. The fifth property (potential for smoke obscuration) is of value because it serves to indicate the smoke load of materials. The final property (fire resistance) should not be confused with the preceding five as it concerns the ability of a building component or assembly (rather than a material) to resist the spread of fire and, as such, it is an aspect of containment and will be considered in more detail in Chapter 5. The structural elements of the building (walls, floors, roofs, ceilings, beams etc) should never be potential fuel sources because they need to remain in place both for structural stability and to contain the fire. Where the structural elements do become fuel for the fire, as with the Oroglass used at the Summer-

26

Fuel limitation

land leisure complex, a major disaster can occur. The fire resistance of structural elements will be considered in Chapter 5 under fire containment. The interior finishes on walls and ceilings are more likely fuel sources and need to be carefully selected by the specifier. If they are heated by a small fire, the linings can (because of the large surface area) rapidly spread the fire by the radiant heating of more distant materials. Good finishes include: • • • • • • • • •

brickwork blockwork concrete plasterboard ceramic tiles glazing plaster finishes woodwool slabs vinyl wallpapers.

Finishes to avoid or treat with caution include: • • • • • • • •

timber hardboard particleboard (chipboard) plastics decorative laminates wall and ceiling linings heavy wallpapers fibreboard.

It is possible to use flame-retardant treatments to improve the safety of these materials, either by surface application or impregnation. The suitability of such treatments is always dependent upon their durability and their proper application. The fire properties of any interior finish are influenced by the materials behind the surface finish, and it is essential that the architect not only specifies the finish, but also the substrate with fire safety in mind. This is a particular problem in the upgrading of existing buildings, where it is not always easy to remove existing finishes. The King’s Cross underground station fire in 1987 provided a graphic example of the dangers of regularly adding new coats of paint over an extended period of time. Certain plastics can be extremely difficult to test because they soften under heat and may even melt. If this happens before ignition, then they will not contribute significantly to fire spread, provided they fall away from the fire. However, materials which ignite before falling can encourage very rapid fire spread. The performance of plastics may depend on fixings and the sheet thickness, as well as the nature of the plastic.

27

Prevention

2.2.2 Building contents A high proportion of fires start by the ignition of the building’s contents. So where the provision of textiles, furnishings or furniture is under the control of the design team, it is important that their contribution to fire prevention is considered. There is a separate set of terms and tests relating to fabrics and furnishings and these can be confusing to architects and specifiers. The ignition sources in tests are numbered, with a smouldering cigarette being source 0 and a lighted match source 1, and so on. In buildings where people sleep, or where large numbers gather, upholstered fabrics should be to the standard of source 5 a medium-sized crib. Hazards arising from the burning of furniture, furnishings and fittings depend upon their construction and, in particular, the types of padding used. There is no truly “flameproof” material and the architect or specifier can only attempt to minimise the hazard by careful choice of furnishing fabrics and foams. The particular dangers of polyurethane foam have already been mentioned in the context of the Manchester Woolworth’s fire. This material presents a very serious hazard, because as it burns, large amounts of highly toxic smoke, including carbon monoxide and hydrogen cyanide, are produced. It also releases large amounts of heat and will melt to form burning droplets. “Combustion Modified” foams are now widely used, which will burn more slowly with a corresponding reduction in the production of heat and smoke. The material is either used as a barrier around an ordinary form core, or it can be used on its own. Polypropylene stacking chairs have also produced fires which a give similar quick release of heat and smoke, due to toxic gases produced by the polymer and the enhanced burning characteristic of the stacking arrangement. Care should be taken to specify stacking chairs which meet ignition source 5. Fabrics are classified by their flame retardancy. Some artificial fabrics are misleadingly described as flame retardant as they do not burn when a flame is applied, but melt away to leave a hole which can expose the foam or filler below the fabric. Cotton fabrics can be treated with Proban or Pyrovatex to give good fire retardancy qualities, so that they can char in the contact zone, but remain in place. It is important that all fire-retardant fabrics are clearly marked with their laundry instructions, so that the retardancy is not removed by washing. In addition to the furnishings and fittings, other of the building’s contents can add to the fuel load, notably any goods stored in connection with the building’s use. It is obvious that there will be increased hazards with designated warehouses or the designated storage areas within buildings, but the architect must also consider the unplanned storage of goods in other spaces. The design team can play a role in controlling the position of fuel hazards, just as in the control of ignition hazards. Once again the objective has to be to separate life risks from potential fuel sources. The total amount of potential fuel within buildings of different types should determine the level of containment provided, and this will be consid-

28

Fire safety management

ered in greater detail in Chapter 5 (Tables 5.1–5.3 relate likely fuel loads to the fire resistance necessary for structural elements and the maximum sizes of components). 2.3 Fire safety management Larger buildings may require more than just a simple maintenance manual and architects may well find themselves involved in the preparation of the fire safety strategy, once occupied. This strategy should already be implicit in the design, and the documentation will describe the decisions the design team have already made on ignition prevention and fuel limitation. The fire strategy will also extend the consideration of fire prevention to include the fire safety management of the building (including communication, escape, containment and extinguishment). Buildings such as hospitals, shopping centres and large industrial sites will need to have such a site strategy prepared as part of the commissioning process, and the architect will probably need to have an input into the document. The fire safety strategy will set out both the normal safety procedures for the building and the action to be taken in the event of a fire. The normal safety procedures will broaden the maintenance schedules into a programme for full and regular fire safety checks of the building, in which all the fire safety systems and components are regularly reviewed. Such an audit allows new risks within the building to be identified and appropriate measures taken to counter the dangers. Any large building will gradually be altered, adapted and modified. Such regular audits enable the fire safety provisions to be modified to cope with such changes. In addition, the normal fire safety procedures will specify the training which the staff will require, both induction training for new staff and regular refresher training for all occupants. Such training will be more than merely “fire drills”; it might also include awareness training in fire prevention and possible special training for particular groups (eg those responsible for managing stores or high ignition risk processes). The second part of the fire strategy will cover action to be taken if ignition does occur, and the design team should be involved in the pre-planning of such action. The document will have to outline the responsibilities and duties of the staff, indicating which tactics should be attempted in what eventualities (refuge or egress, fire extinguishment or fire containment, etc). Such a pre-planned response to a fire incident can be used as the basis for training and should also be adjusted as the fire safety audits reveal new risk or modifications to the building in use. Having examined the measures the architect can take to maximise the chances of preventing a fire, it must be remembered that this tactic can never by 100 percent effective and that it has to be assumed that ignition will occur within the life of the building. Chapters 3 to 6 consider the post-ignition tactics that can be attempted and which will have to be integrated into the building design.

29

Chapter 3

Communication

When fire breaks out, it is essential that it is detected as soon as possible. The exponential rate of fire growth has already been stressed in the first chapter, and it is obvious that the earlier action can be taken to mitigate the consequences of ignition, the greater the possibility of success. Once a fire is detected, either by the occupants or by automatic means, it is then necessary to communicate the location of the fire to the occupants and the fire service. The information will enable any prearranged fire evacuation strategy to be instigated and trigger any automated response; such as an active smoke control system, closing fire doors or triggering a suppression system. It is important that designers think of the communications system as a whole rather than as an isolated piece of engineering added to the completed design at a fairly late stage. Rather, the system should be specifically designed to relate to the nature and form of the building. It must form a network from the discovery of the fire to the information being delivered to each occupant, the fire service and the building management. Although a fire alarm system is part of the communications, it is generally classified by its principal purpose as being either for life safety (L) or property protection (P). Some systems may be regarded as offering both life safety and property protection (L/P). Any system which is solely described as manual (M), relies solely on manual activation of the alarm and cannot be considered a comprehensive system, although it might be appropriate in a few very small or specialised buildings. Despite such classifications, all systems will provide some alarm to initiate fire escape and to attempt fire containment and extinguishment. 3.1 Detection Fire detection systems identify the products of a fire. For a person this is by sight, sound or smell, and for an automatic detector it is by heat, smoke, light (in ultraviolet or infrared wave lengths) and by turbulence movement. The detection devices sensitive to these different effects will be considered separately.

30

Detection

3.1.1 Manual People are probably the best “smoke detectors” present in buildings, although dogs are undoubtedly even more sensitive. People are able to recognise fire by its sound and smell, and by sight, and then to quickly make a rational judgement. The designer can make a positive contribution to fire safety in the design of circulation routes and certain types of accommodation. By achieving good passive surveillance of the building by the occupants fires will be prevented, or at least detected earlier. This is most relevant when positioning the security point, the janitor’s or porter’s room, the siting of a nursing station, or a supervisor’s office. It might be worthwhile planning the circulation routes of large buildings such that all areas are under passive surveillance. This might mean that staff have to pass through the warehouse on their way to the canteen. However, this desire to achieve passive surveillance may conflict with the need to achieve fire separation (e.g. between storage and office areas). It must also be balanced against the risk of increased ignition which comes with allowing more people access to more areas. It is equally important that designers avoid if at all possible circulation routes which are only used for fire escape and are normally deserted. Such areas will not be under regular surveillance and a fire in such areas may not be detected quickly. They may also become dumping grounds for stores or rubbish, such materials not only posing a fire risk, but also hampering evacuation. Fire safety training emphasises the need to raise the alarm as the first action, but the most difficult problem for the trainer is to balance this with the need to move away from the fire as fast as possible. In the domestic situation to get everyone out and then make a telephone call to summon the fire service is the correct action. In non-domestic buildings the same principle normally applies evacuate first and then summon the fire service. However, if a fire-alarm system is provided then an alarm can be raised by using a “break glass” call point. These manual call points take the form of a red box often with a clear plastic sheet etched to provide an easy break. It is usual to position these on exit routes, encouraging people to leave the building and ensuring that no one has to move towards the fire in order to raise the alarm. In some buildings, such as care homes or hospitals, additional call points are required where the nursing or staff base is located. Similarly, a security post or night porter’s position should also have a manual call point. Good observation by staff in warehouses, factories and sports areas will contribute to good fire safety through rapid detection and the early elimination of potential sources of fire. However, manual detection will only be of value while the building is occupied and it may well be necessary in such buildings to install automatic detection to provide cover at night. In restaurants, clubs and public houses it is wise to consider siting the call points so that they are under staff control and any risk of malicious, or just stupid, activation by intoxicated customers is reduced. This design decision will need to be integrated with the fire safety policy and procedures for the establishment.

31

Communication

3.1.2 Smoke The most frequently used automatic detectors are activated by the smoke particles from a fire, and these are normally able to react at an earlier stage than heat detectors. There are two main types: ionisation and optical. Dual heads with both detectors are also manufactured. The ionisation detector is the most sensitive to small smoke particles and will probably react more quickly at the early stages of a fire. The optical detector depends on the smoke particles scattering the passage of a light beam within the detector head and is therefore more sensitive to larger smoke particles. In principle, ionisation chamber detectors work by monitoring the electrical current between positive and negative plates across an air gap, in the presence of a very small radioactive source. The radioactive source causes the ionisation of the molecules in the air, ions are attracted to the respective oppositely charged plates and a modest current then flows. The introduction of smoke particles will reduce the current flow and when this is sufficiently reduced or the voltage drop replicates the kind of performance expected in a fire, the alarm is initiated. In practice, smoke detectors are usually more sophisticated than this and can compare results between a closed chamber and an open chamber. However, they are extremely sensitive to small smoke particles and are particularly good at sensing a fire in its initial stages. Ionisation detectors are normally ceiling mounted and provide coverage for about 100m2, provided there are no obstructions. Smoke in an optical detector interrupts a beam of light from the source to the light trap and deflects some to the photo-electric cell. The current generated by the cell is monitored or has a pre-set level, which when reached initiates the alarm. Such light scatter detectors are more adept at sensing dense smoke, while the ionisation detectors are more sensitive to the smaller, normally invisible, smoke particles produced at the start of the fire. Therefore optical detectors are better if smouldering fires are anticipated, and ionisation detectors if the danger is flaming fires. Care is needed in the siting of all detector heads and they will normally be in the highest point in any space. However, smoke modelling may suggest alternative locations if there is any risk that smoke may not fully rise, or in buildings with a particularly large volumes (e.g. churches). Locations near exhaust extracts and fresh-air inlets in kitchens and garages should be avoided. As a very simple rule in non-domestic buildings it is better to site ionisation detectors in rooms and optical detectors in corridors and circulation routes. In their own home most people are now familiar with devices which detect smoke. These are normally combined smoke detectors and alarms which serve both functions and consequently should be more accurately described as smoke alarms, sometimes called single station smoke alarms, rather than detectors. They are normally very basic ionisation chamber designs. They can either be completely independent and rely solely on a battery, or be linked to the mains supply, with a battery in case of mains failure. If battery operated, then it is

32

Detection

essential that the batteries are replaced regularly, and if mains wired it is essential they are not disabled when the back-up battery begins to emit a warning that it needs to be replaced. Most have a test button and it is sensible to install them in positions where the test button can be actually reached, rather than at the top of stairwell where the average householder cannot reach it. If mains wired there is then the potential to wire a number of smoke alarms together to cover a larger dwelling. The installation of simple smoke alarms has spread rapidly throughout Great Britain in the last 25 years, from 8 percent of homes in 1988 to 86 percent of homes in 2008. This may be one reason for the steady decline in fires, death and injuries in recent decades. However, in 34 percent of the dwelling fires in 2011/12 there was no smoke alarm present. Even in the dwelling fires where there was an alarm it is disturbing to note that in over a quarter of cases the alarm did not operate and in a further sixth, although it did operate, it did not raise the alarm. It has to be realised that these statistics are based on the fires attended by the fire service and that therefore they do not include fires which are identified sufficiently early for the occupants to deal with them without outside assistance (source: Department for Communities and Local Government, Fire Statistics, Great Britain 2011 to 2012, sections 2.25–2.28). Initially most domestic installations were battery operated, simply fixed in existing houses, but now mains wired systems are required by many jurisdictions in new houses and often in rental properties if they require licensing (e.g. houses with multiple occupation). 3.1.3 Heat Heat detectors are general-purpose detectors which react at a designated temperature or to a prescribed rate of rise of temperature. The early heat detectors used the expansion properties of bi-metallic strips to bend under heat and in its simplest form consisted of a bimetallic strip which bends so that at a fixed temperature it allows an electrical contact to close and initiate the alarm. Many of the heat detectors currently on the market use small electronic resistors calibrated to temperature sensors rather than a metallic strip. A normal operating temperature of such a detector might be 68oC and each might cover an area of 50m2. The early ‘rate of rise’ detectors incorporated both a fixed temperature detector and additionally relied on the elative expansion of two different bi-metallic strips. A rapid rise in temperature caused one strip to expand to make contact with a point held in place by a second strip shielded from the ambient conditions. The second strip was, however, allowed to expand with the ambient conditions, so a slow rise or fall in temperature would not cause a contact. The latest detectors achieve the same effect using electronic temperature sensors. A fixed temperature sensor is also always included to allow for fires which have an exceptionally long, slow burning development. The disadvantage of a fixed temperature head is in its relatively slow response time, the fire may have spread significantly before the trigger temperature is reached. A rate of rise detector should respond more quickly. Fixed

33

Communication

temperature detectors can, however, be more suitable in locations where frequent temperature fluctuations might otherwise lead to false alarms, such as kitchens and laundries. While smoke detectors will normally give a faster indication of a fire, heat detectors will be preferred in situations where there is a risk of false alarms due to dust or other pollutants in the atmosphere. This is particularly true of kitchens, boiler-rooms, car parks and many factories. 3.1.4 Light Infra-red radiation and ultra-violet light sensors can be used to detect flames even when not visible to the human eye, and these can be used for more specialised forms of detection. Such detectors use the radiant energy from the fire in the infra-red or ultra-violet spectrums to react respectively to either a photoelectric cell or a gas-filled sensitive tube. The infra-red detectors are usually further adapted to respond to a flickering source to avoid false alarms from electric heaters or sunshine. They can used to sense through smoke, but may not pick up certain fires which burn with a clear (sometimes transparent) flame (e.g. alcohol or isopropanol). Ultra-violet light does not penetrate smoke readily, but it will be sensitive to clear flame fires. There is the danger, with both infra-red and ultra-violet detectors, that they may respond to very bright, or indirect, sunlight. Therefore the siting and calibration of detectors is critical. Where the contents of a building are likely to produce smoke, or to smoulder before flames appear, flame detectors probably are not suitable and smoke detectors will normally be adequate. However, flame detectors are highly suitable in areas where there is the storage of flammable liquids in any appreciable quantity. Flame detectors have also been used in large volume spaces, such as cathedrals, where it is difficult to predict smoke behaviour because of the complex geometry and significant risk of cooling preventing the smoke reaching the highest points. Small fires can therefore be picked up quicker in these situations as the flame flicker may be pronounced. 3.1.5 Thermal turbulence Most of the detectors already described are point detectors, that is they identify smoke, heat or light at a particular point or within a fixed radius of that point. Thermal turbulence detectors depend on beams which optically sense hot air currents or moving smoke and interruption of a light beam triggers the alarm. These detectors are extremely useful for large volumes, especially atria and highceilinged spaces. They can be positioned so that they cross the space at different levels, which can be important if there is a risk that the smoke might cool and stratify before it reaches the highest point. Garages for public service buses can present a particular problem, as accidental or deliberate fires might be left smouldering within individual vehicles. While it would be impossible to install detection in each bus, a beam

34

Comprehension/analysis

detector can be used sited to pass through the windows of each vehicle in a line. Obviously this only works where they are left parked in the desired geometric arrangement and the vehicles are themselves of a standard design. However, this system was used to tackle the problem of terrorist attacks with incendiaries left on buses during “the troubles” in Northern Ireland. Optical beam detectors have been recommended for use in cathedrals and large churches, where there can be problems with small fires in a large space. In this case there might be sufficient energy to carry the smoke plume up to the ceiling and a reservoir of heated air at a high level gives the possibility of the stratification of smoke. The siting of detector points or beams is a specialist task and in such instances assistance will be necessary from an engineer who specialises in smoke modelling. Some detectors of this type use infra-red beams sent from a source to a receiver. The thermal effects of the fire will cause the beam to be interrupted or modulated at the receiver. Should the fire develop to obscure the beams at an early stage, this will trigger an alarm signal. The beam detector is a therefore available to detect both heat and smoke. There are disadvantages with the system, the possibility of accidental interruption of the beam or building movement. The normal maximum length of a detector beam is 100m. 3.1.6 Smoke sampling In some special situations use may be made of smoke sampling systems, where air is drawn in sequence from a variety of fixed locations and passed through a sensor. There may be advantages in using such a system in secure establishments (prisons, secure hospitals etc) where the occupants might be tempted to interfere with more conventional point detectors. The air is usually drawn along small-bore sampling pipes to a central monitoring station, which then uses smoke detectors to sense any smoke particles in the sample. Also available are adapted optical smoke detectors, known as optical duct sensors, which can be used to sample air from the return ducts of an airconditioning system. These detectors have been adapted to suit the particular width of the duct. They are particularly valuable in preventing smoke spread through re-circulated air. 3.2 Comprehension/analysis Having detected a fire, it is then a question of interpreting the signal. The various detection devices can be used to give a simple fire condition signal, while a manual call point is a simple switch which gives a signal when activated. Detection can also be used to signal a pre-set level of temperature or smoke level. Fire alarm systems which work in this way are termed conventional systems. It was apparent to many engineers that such “conventional” systems discarded much of the data that was available from the various detectors and sensors. The advent of small reliable microprocessors made it possible to analyse the results from

35

Communication

each device in a system and obtain information on the performance of individual detector heads to give both greater accuracy in the analysis of effects and an ability to predict and discount false alarms. These are termed addressable systems. 3.2.1 Conventional systems In a conventional system (see figure 3.1) each fire compartment or subcompartment will be portrayed as a “fire zone” on the control panel, with the detectors wired to identify the “fire zone” where the detector operated. In a multi-zone building a conventional alarm panel will list a number of zones, often with a location plan of the zones displayed alongside. The information on the panel is therefore limited and in the event of an operation it is necessary to go to the fire compartment or sub-compartment to determine to establish the source of the fire or possibly the faulty detector. While in the terms of compartmentation a large space may be quite acceptable due to a low fuel load, this might not be acceptable in terms of locating the fire or searching for occupants, so in these cases it will be necessary to sub-divide compartments into a series of fire zones, or use a system of local panels within zones. 3.2.2 Addressable systems Addressable systems (see figure 3.2) developed in the 1980s with introduction of microprocessors and have rapidly come down in price with the information technology revolution. They use the same number of detector devices and call points as conventional systems, but differ in that they can provide far more information. Most importantly they can compare the data being received with what is stored in the memory. The status of each detector can now be monitored

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36

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to identify changes and patterns. It is therefore possible to separate out some fault readings from a positive fire detection. The various components of the system can all be controlled on one wiring loop as the system in use interrogates each device in turn. They are inherently flexible and so could be set to scan manual call points more frequently than automatic components or other devices, if that is appropriate. Alternatively the settings for alarm can be varied by the day of the week or the time of day. It is still necessary to relate the fire information to the formal fire zone, but this time it should be possible to relate the fire information to the fire compartments or sub-compartments, as such it will be possible to identify the detector or device which is providing the signal. Individual devices can be excluded from the system if they known to be defective or if there is experience of faulty signals, given different trigger levels. Therefore the amount of information available is much higher. While the capital costs of an addressable system are likely to be higher, the difference is much less than it used to be and the design team will need to consider the advantages in terms of installation, operation and maintenance. It is also possible and increasingly common to integrate an addressable system with other systems (security, environmental controls etc), although it is essential to protect against a fire alarm signal being corrupted or delayed by the operation of other systems. It is increasingly common to go further and incorporate microprocessors at the detector head, so-called smart detectors. This allows even greater control and precise setting of individual heads. This is particularly important

37

Communication

where the building contains different ambient conditions, for example both dusty workshops and air-conditioned offices, or both cool and hot working environments. Systems can also be set to give further signals which might include faults, or pre-warnings. It is always necessary to allow for the commissioning of systems, but this is critical with addressable systems. In the commissioning process time should be allowed for the proper inspection, earthing tests, operational tests, and testing of each device for “fire”, “fault” and “safe” settings. It is normal practice to ask for certification of the commissioning process for the benefit of the client, insurers and the inspection or licensing authorities. 3.3 Alarm The alarm when raised is a signal for occupants to evacuate, or to be alert in preparation for evacuation. The alarm should also result in the fire service being summoned, so that they can start fire-fighting and, if necessary, assist in the evacuation. It is crucial therefore that an effective system exists, and the designers should think carefully about the function of the alarm in relation to the use of the building. 3.3.1 Occupants The most common form of fire alarm sounder is the electric bell. It has the advantage of being universally recognised, and its sound can carry throughout a building. It can ring as an intermittent pulse or a continuous sound, perhaps signifying respectively alert and evacuation. Where the building or site is large or there is a high degree of background noise then it might be more appropriate to use a siren. Where there will be a significant difficulty in hearing an alarm, perhaps because of noisy machinery (e.g. factory) or occupants with impaired hearing (e.g. care home) then a visual signal might be needed, for example flashing lights. In a number of nightclubs and music venues where it would be impossible to attract attention by bell or siren the opposite approach to alarm is taken and on evacuation being required all sound systems are switched off so that it is the silence which indicates an emergency and only after that has been established are instructions given. In some nightclubs this is complimented by changing the lighting so that it is uniformly bright and even. Where people are asleep the problems of alerting them to fire are even more serious and in hotels, hall of residence and other such buildings louder bells or sirens are needed. In countries where these are not mandatory there have been serious fatalities and survivors of the 1990 fire in the Cairo Sheraton hotel complained that the first indications of the fire in the hotel complex were the crackling sounds of the fire itself and the noise made by other guests as they fled. The hotel had a large number of guests, many of whom would not have been familiar with the building’s layout. The fire occurred in the early hours of

38

Alarm

the morning and the lack of the alarm system meant that many were not roused until the fire was well established. In domestic fires which develop during the night the presence of selfcontained detector alarms is critical if those sleeping upstairs are to have sufficient warning of a fire which may well be developing downstairs in the kitchen or living room. Before the widespread introduction of such alarms the first warning the occupants might have was the crackling sounds of a well-developed fire, which often meant that the stairway was already smoke logged and unusable. In some building types it might be necessary to warn staff in advance of the other users, either so that they can begin to prepare even before it is certain there is a fire which will require full evacuation. In shops and shopping complexes the alarm may also need to be more sophisticated than a bell or siren. The initial alarm or maybe a pre-warning might take the form of a coded message, for instance asking staff to check a particular department, or for shoppers to leave as sprinkler testing is about to start in a particular department. This can alert staff to the existence of a fire and, more important, its location. With such sophisticated alarm messages it is essential that these are tested in drills. Should the fire continue to grow then a full evacuation and a more conventional alarm signal might be used. In hospitals, care homes or institutions, where the problems of moving sick or immobile patients is balanced by the special training and the availability of large numbers of staff, such pre-warning is essential and any evacuation is likely to be phased with staff concentrating on those most at risk. Therefore information and alarm might well be provided through staff call and alert systems, rather than simple sounders. In hospitals and prisons it is normal to evacuate initially the fire compartment/zone of origin as stage one in the fire plan. Visitors are usually asked to leave the building, while other occupants make their own way or are assisted to a safe refuge. Conventionally, in these instances, fire alarm bells ringing continuously for evacuate or intermittently for alert/standby, are used. However, coded messages are also sometimes used; for example, one American hospital requests “Dr Red” to go to the department where the fire has started. Public address systems obviously permit more detailed instructions to be given and so can be very beneficial; however care has to be taken if more than just pre-recorded messages are to be used. Allowing someone in a fire situation to give information directly to the occupants in real time is risky unless that individual has a full understanding of exactly where the fire is and what is the appropriate escape strategy for this strategy. It also requires that there is somewhere in the building where a member of staff can safely remain to give such messages. To simply assume this can be done from a security centre is dangerous unless the choice of that building has been carefully made so that it will remain safe in the event of a fire. There have been tragic incidents where someone not sufficiently informed of what is happening has given instructions to the occupants, which has led to more deaths (e.g. the Summerland fire). Buildings where family groups tend to be in separate areas such as shopping centres where

39

Communication

children might be left in a supervised crèche pose an additional risk, and it is important that parents are reassured by pre-recorded messages that their children will be evacuated separately to a place of safety outside the building where they can be collected. A further problem in shopping centres with multi-storey car parks is the possibility of shoppers attempting in large numbers to return to their vehicles and exit with them, risking a jam in the car park with people becoming trapped, and those vehicles which do leave blocking the surrounding streets preventing fire-fighting vehicles gaining access. Again, pre-recorded instructions can be given telling drivers they must leave directly and that cars can be collected latter. 3.3.2 Fire service For most buildings, an ordinary telephone call will suffice to inform the fire service and the priority of making such a call will be part of the fire response plan and there should be a clear understanding about whose responsibility it is to make such a call. If it is a building with a staffed switchboard, then they have a role and it is important to have a ready prepared message for the caller to read setting out the full address, telephone number and any access instructions. Even where there is an automatic link to the fire service through an alarm management company triggered by the detection system, there should still be a back up phone call in case of failure. The provision and siting of any fire alarm panels or sub-panels is also important. They should be located to take account of the pre-planned fire strategy, the need for those responsible to be informed and for information to be readily available to the fire service when they arrive. This normally means close to the main entrance, or the entrance most designated as the arrival point for the fire service. On large and complex buildings it is very helpful to have a repeater panel in case the location of the fire makes the main panel hard to reach. The fire alarm system can also be used to activate other systems. For example to release door hold open devices so that all fire doors or shutters in the building will slowly close, to operate motorised ventilation and smoke extract systems, to summon staff through a call system or to operate fire-extinguishing systems. In the case of ventilation systems where life safety has to be considered, it is normal to allow for automatic shut down, or to limit input air while the extraction systems are left running. This can reduce the probability of the smoke and fire being spread by the ventilation systems. During the MGM hotel fire in Las Vegas, in 1980, the continued operation of the heating and ventilation system spread the smoke and fire to other floors. The fire had started in the restaurant servery and it initially spread rapidly through expansion and seismic joints, and then through the air-conditioning system. There was no automatic fire alarm system, despite the building being 22 storeys high and containing a variety of high-risk areas. Although the fire was brought under control within one hour, 85 people died.

40

Signs and fire notices

The ventilation system should be so designed that the fire service can shut off the extract air or switch back on the supply and extract air from a control panel. This, like the fire alarm panel, needs to be in an easily accessible position and clearly labelled identifying essential and non-essential plant. 3.4 Signs and fire notices 3.4.1 Signs Signs are extremely important in giving good information to the occupants and the fire service in non-domestic buildings. However, they should not be over used as there is a real risk that over familiarisation can lead them to be ignored. In instances where the circulation routes and exits are obvious and the occupants are familiar with the building, they may be unnecessary. There is obviously no value in installing them in dwellings or where people live permanently (such as houses in multiple occupation, residential care homes and long-stay institutions). Signs are essential to mark exits which are not part of the normal circulation routes. In public assembly buildings they should indicate all available routes. These signs would be rectangular with white wording on a green background; when illuminated, the contrast is frequently reversed. Any other information which relates to a safety practice or circumstance would be similarly coloured. For example in buildings where progressive horizontal evacuation is used, doors are marked to indicate their status (Figure 3.3). In places where there are lots of other signs, such as shops, conventional fire exit signs may not be sufficiently noticeable to offer any help. In these instances alternative methods of identifying and directing people towards exits should be adopted. There are a number of shopping centres which now use very bright directional spotlights, which are activated in an emergency and highlight escape routes, even when there is visual confusion and possibly poor general illumination. In spaces with deliberately low levels of normal lighting a simple

-* GfttdN. mm.

J W / 2 0 N 7JU, m CU AT/Q N

nou7&.

H0/1/20NTAL m < M T M

naam WnOOGH m u . m u.

3.3 Fire escape signs: safety colour green, shape rectangular

F f e © x HH WV/7F OGTTtfiJNG o n G n e tH 3A c m n o u N D .

41

Communication

way of alerting people to an emergency is to dramatically increase the lighting levels throughout the premises on the detection of a fire (e.g. in bars and night clubs). If there is also likely to be a lot of background noise, as in music venues or clubs, then the combination of bright lighting and the immediate cessation of all music will provide a much more effective form of alarm than any normal alarm bell or siren and is likely to have a greater impact on the occupants. Signs which are necessary to indicate actions that must be taken are “mandatory” signs. These signs are circular with white wording on a blue background. The most commonly seen is the “Fire door – keep shut” instruction (Figure 3.4). There may be a need to warn both the occupants and fire fighters of hazards within the building (e.g. radiation hazard and biohazard symbols). These signs have black working on a yellow background (Figure 3.5).

/ Fire door \ keep locked \

shut

& M fr C J/tCC f J

/Automatic\ i

Fire door

Fire door \ keep shut./

\keep deary

- w w r t-

. rn rre o a c m m u n d .

u rrm w .

3.4 Mandatory signs: safety colour blue, shape circular

C a u tio n ris k o f io n i s in g r a d ia t io n

m a n Of/0N/7TH6 MO/AT/ON.

c a u t io n

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CAUTION niSM Of-

AW:

3CACH TMANGC&S, YMLOW AAOiGfiOUNC M A C* / U (/STRATTONS.

42

CAUTION flIS K Of6I0C06/CAC UATAfiD.

C AUTIO N A ISff O r frOGCTfi/C SMOCK

3.5 Hazard warning signs: safety colour yellow, shape triangular

Signs and fire notices

Some signs may prohibit action (e.g. No smoking). These signs are a red circle with a diagonal bar and a black pictorial symbol on a white background (Figure 3.6). Red has been retained as the colour for fire equipment signs because of the obvious association and historic familiarity with fire (e.g. “Dry riser” and “Fire point”). These signs should be rectangular with white wording on a red background (Figure 3.7). All signs which give critical information should be able to be read in different lighting conditions, both normal and if a fire occurs. It is usually sufficient to ensure that light will fall on to the sign, but in situations where the building might be used in darkness (e.g. theatres) such signs may require internal illumination. 3.4.2 Fire notices In places of work and institutions it is necessary to have a prearranged fire evacuation strategy. As well as training the staff, well-thought-out concise instructions in the form of a fire notice need to be posted at suitable locations. These need to include the actions to be taken on discovering a fire and the details of the evacuation plan relevant to the particular fire compartment including any designated

an a * an a *

Stop. do not enter when the red light is on NO SM0KJN6.

3.6 Prohibitory signs: safety colour red, shape circle with bar

» K > & A C K & H X /H P m m u ttv u n o .

Fire point

D ry riser

Foam inlet /

3.7 A fire safety notice: safety colour blue, shape rectangular

^ m o M C K & n o u N O - w / jr e - o o n o t n - m m - c t r r e r s / H t r . s

43

Communication

fitufr c/ficce-.

3.8 A fire safety notice

rW U/7r C& TTM /N G .

F ire action]

3 U J6- &ACM QROUND m / T S - L6 7 T to J N G . -

W W Tfr r C& TTM /N G .

1 Break glass of nearest fine y'' alarm. 2 Close doors near the f ire 3 Move everyone to a safe place

assembly point (Figure 3.8). It is now customary to also mark these assembly points with the standard graphics so that it is easier to establish if everyone has successfully left the building should a fire occur.

44

Chapter 4

Escape

Every building should be designed so that the occupants can escape when fire breaks out. To escape they must be able to reach a place of safety without being overcome by the heat or smoke, and therefore the time need to escape has to be shorter than the time it will take for the fire and smoke to spread. This can be achieved by controlling fire spread and by ensuring escape routes are neither too long nor too complex. Consequently, escape must be designed into the circulation routes within the building and must form an integral part of the initial concept of the design. It is not sufficient to consider the means of escape simply as a series of protected routes down which people can escape by their own efforts from any point in the building to the outside. While many people can escape by their own efforts, a wide variety will need assistance. For others it might be unwise or unsafe for them to just go outside (e.g. wheelchair users, very young children, those in prison or care homes). In large and complex buildings the outside might be a long way and in high rise buildings many floors below where the occupants start. For these reasons there are two escape strategies, the simple egress (direct escape to the outside when the alarm sounds) and refuge (the use of the structural fire containment of the building to provide a place of safety within the building). With refuge escape initially only needs only to be from the compartment where the fire originates to an adjoining safe compartment from which there is the chance for further escape if that becomes necessary. There is also a third strategy which may be necessary as a last resort and should be designed for, namely rescue by persons working from the outside of the building. This is not necessarily reliable and should never be considered as the sole or even first choice, but it may be the last resort if other escape routes fail. 4.1 Occupancy In designing the means of escape from a building the starting point has to be the likely occupants and their predictable behaviour. An understanding of their 45

Escape

characteristics will suggest their speed of movement and in conjunction with the expected speed of the fire spread, enable the design of an acceptable means of escape. Crucial to the design of escape routes is this appreciation of likely speed of fire spread as explained in the Chapter 1. During the bush and scrub fires in southern France, in 1989, a French firefighter recorded seeing a fire overtake and consume galloping wild horses. Inside buildings fire spread can be equally startling; the television filming of the fire spread as it happened at the Bradford City football ground in 1985 made this clear to the general public. The nature and number of the occupants is probably more influential than certain of the physical design factors emphasised in some escape codes and guidance. It is the interaction of the communications system with the occupants, the effectiveness of the signposting, the clarity of the internal layout and routes, the quality of the fire safety training and the response to emergency which will minimise the life risk from fire. Five key characteristics of the occupants can be identified and will now be described: 1. 2. 3. 4. 5.

sleeping risk numbers mobility familiarity response to the fire alarm.

4.1.1 Sleeping risk Buildings where people sleep are inherently more dangerous than those used only by people who are awake. This is the single most important factor to recognise for the architect involved in the fire safety design of a building. Where people are asleep there is the chance for the fire to grow before discovery, and even once discovered the reactions of people who have just been wakened will be much slower. Many a fire is prevented from being nothing more than a minor incident by prompt action of simple extinction. Moving the clothes dryer further away from a heater when things smell hot, quickly removing the glowing cinder that spits from the fire on to the carpet, are familiar examples from normal domestic life. The combination of lack of preventative actions and the slow response time to a fire make sleeping risk the critical factor in determining escape strategy. The vast majority of fire deaths occur in people’s own homes, simply because of the added risks when they are asleep. Hence the key role played by simple smoke alarms in reducing fire domestic deaths as discussed in the previous chapter. Residential premises, whether institutional (e.g. boarding schools, barracks) or commercial (e.g. hotels, hostels) also pose a severe risk. In institutional premises there may be staff awake and on duty all night, but automatic detection is also an essential safety feature. All commercial residential premises

46

Occupancy

of whatever size should have automatic detection in the bedrooms. The Fairfield Old People’s Home at Edwalton, Nottinghamshire, was severely damaged by fire in 1974, and 18 people died. The fire was thought to have been started by one of the residents smoking in a bedroom, while most residents were asleep. It spread rapidly through the continuous ceiling void and was not detected until an advanced stage. The greatest damage and loss of life ensued at the opposite end of the building. However, the presence of automatic detection is not always enough. In the more recent serious care home fire at Rosepark in Uddingston, North Lanarkshire in 2004, 14 people died. This building had automatic detection, but when this activated the staff had not been properly trained and instead of taking it seriously attempted to discover the cause, but misunderstanding and searching the wrong floor concluded it was a fault and tried to reset the alarm panel. Even when the fire service attended there was confusion about the best access to the building and the location of the fire, while residents died from the smoke and toxic gases in their bedrooms. Following this fire three full-scale reconstructions were conducted on an exact recreation of the affected floor. The first recreated the situation exactly as it had been on the night of the fire and was able to show precisely what had happened and enable the fire spread process to be studied. In the second recreation the same was fire started, but with all the bedroom doors closed. In the third test a life safety sprinkler system (see Chapter 6.2.2) was installed. In the latter two tests it was clear that the number of fatalities would have been reduced, though not completely eliminated by those precautions. The hotel fires of the later 1960s, particularly the fire at the Rose and Crown in Saffron Walden, Essex in 1969, in which 24 died, were instrumental in ensuring the designation of hotels and boarding houses under the Fire Precautions Act 1971, which for the first time began to systematically apply fire safety standards to classes of existing buildings. 4.1.2 Numbers To plan an adequate means of escape the designer needs to know how many people will be in the building and where precisely they are likely to be located. This will depend upon the building’s function, but architects must remember that a building designed for one purpose may well be used for another. For example, in one award winning Hampshire school the fire service were horrified to find that the double height “street” down the middle of the building was not just used for daytime circulation as had been expected, but was being used for evening activities as diverse as beer festivals. Some buildings are designed to hold a maximum number, for example a theatre or a restaurant, but for others it is necessary to make an estimate of the maximum numbers that might be using the space. This will be particularly important for any large numbers of the public whether for pleasure, work, travel or shopping. In the planning stage it is helpful to do this by making an estimate of the likely maximum number of people for the specific building type

47

Escape

using an “occupancy load factor”. These factors are based on the experience of how close people are prepared to be and what has been found can happen at maximum crowding. The occupancy load factor is safer to use than the expected numbers as it makes allowance for the times when the expected numbers are exceeded. Each area can give an occupancy capacity by dividing the floor area in square metres by the occupancy load factor and in order to design escape routes from the whole building the maximum occupancies so calculated can be summed. For example, a bar of 50 m2 would have an occupancy capacity of 100 as the occupancy load factor is 0.5. A simple table of occupancy load factors is included for different functions (Table 4.1). This has been derived from first principles rather than from any particular code or guidance document and is intended primarily for student architects working at the design stage. The special problems associated with very tall buildings (over 10 storeys) or deep basements (more than one level) would, of course, need special attention. In the design of flats and dwellings the normal ergonomic requirements of circulation render such calculations unnecessary, however where large number of dwellings may share escape routes then such estimation may become necessary so that sufficient corridor widths, stairways and door widths can be achieved. In the Republic of Ireland the most serious fire in recent years occurred on St Valentine’s Day 1981, when 48 young people died at the Stardust Disco in Dublin. One of the main problems was the sheer number of people in the disco at the time. Large numbers should not have constituted a problem, but combined with a total lack of any form of Building Regulations, inadequate local authority supervision and the untrained owners’ advisers, they contributed to the disaster. The management failed to give the alarm and commence evacuation immediately the fire was noticed. Instead, the occupants watched the unsuccessful attempts of two employees to extinguish the fire. Then without warning it Table 4.1 Building type and occupancy estimation

Building Type

Occupancy

1. Dwelling 2. Assembly and entertainment buildings (a) bars (b) dance halls, queuing areas (c) meeting rooms, restaurants 3. Factory 4. Office 5. Open-sided car park 6. Residential care building 7. Hospital 8. Residential building (other than hospital or residential care) 9. Shop 10. Storage building

Five times bed spaces

48

“Occupancy load factor” = 0.5 “Occupancy load factor” = 0.7 “Occupancy load factor” = 1 “Occupancy load factor” = 5 “Occupancy load factor” = 6 Twice car park spaces Three times bed spaces Three times bed spaces Twice bed spaces “Occupancy load factor” = 4 “Occupancy load factor” = 15

Occupancy

expanded into an inferno with exponential fire spread due to poor seating and wall lining materials and low ceilings. In addition to estimating the total numbers within the building, it is also necessary to consider areas where people will congregate and where there might be serious crowding or, in the event of evacuation, “bottle-necks”. Large numbers of people do not move quickly, or even at normal pace, so it follows that escape must be accomplished in a shorter distance. The designer may need to consider aspects of crowd behaviour and the management of large numbers of people. Escape routes will need to be clear, unambiguous and capable of handling the worst conceivable scenarios. Illumination, signage, communications systems, even crowd control barriers may need to be considered. The potential for disaster with large numbers of people was sadly illustrated by the crushing to death of 97 people at Hillsborough football ground in 1989. Here the surge of people directed into the ground, trapped helpless spectators already on the terraces against crowd barriers and perimeter fencing, with those at the rear of the crowd having no idea of the deaths occurring at the front by the pitch. Provision for escape should have given spectators the ability to move away from the disaster, even if this meant releasing gates in the perimeter fencing to allow access to the pitch. Four years earlier, 55 people had died when the main stand caught fire at Bradford City football ground. Here again the number of casualties was increased by the poor escape routes. The only rear exits were at the highest point and reached by a dimly lit, 2.6 m wide corridor, which was further narrowed by refreshment stands. Unlike Hillsborough, escape forwards on to the pitch was possible and many moved that way, but they were seriously slowed and hindered by two lines of barriers. It is areas where a high density of people can be expected to arise that are usually subject to a variety of legal controls and licence restrictions, partly through such tragedies with the high loss of life. Proper thought and allowance for escape at the initial sketch design stages can prevent abortive and intrusive work to add in escape provisions at the latter stages. 4.1.3 Mobility It has already been stressed that people must be able to escape from the threatened areas before being overcome by smoke and heat from a potential fire. However, people will escape at different speeds and there is no perfect figure which the designer can use. Some of the occupants may be disabled, encumbered or drunk. There have been many attempts to estimate how fast fully mobile, unencumbered and sober people will move and most estimates come within a range of 50–100 m per minute. Therefore a basic figure erring on the safe side for the speed of movement of those without any problems might be 50 m per minute. The worst cases of impaired mobility will be those people who cannot move at all without assistance, such as those confined to bed. Further complications will occur when considering orthopaedic patients with traction

49

Escape

equipment, or those in intensive care on life support systems, or even those currently undergoing operations. The designer of buildings such as hospitals or nursing homes which will have such occupants has got to design to permit their safe escape. As well as people with obvious physical problems which will impair mobility, other people needing to escape may be blind or partially sighted, hard of hearing, or with learning difficulties which mean they will respond more slowly. Such issues may be easily planned for in healthcare designs, but they can just as easily be found in the general population and any place where there are large numbers of people (e.g. shopping centres, theatres) will have to be designed to ensure their safety It may be pertinent in the design of very large schemes or large spaces to seek the assistance of computer modelling techniques to simulate population movements. Airport terminals are a prime example of this and the fire scenario should be one among the many scenarios which is being evaluated at the earliest design stage. The computer modelling of people movement should ideally be linked to the modelling of fire growth and smoke spread and, as always, the key to success is ensuring that time available to escape is greater than the time it takes for the conditions to become untenable. Speed of escape is also affected by the design of the escape routes. People move at different speeds in different situations: through a room with furniture, along an unobstructed corridor or down stairs. Even the floor finishes will impact on the speed of crowd movement. Other problems might occur where there is a need for security, either to keep people in, or to keep people out. In prisons or hospital secure units it may be necessary to plan for the occupants to be only allowed to escape into another part of the building, or a secure compound. However, there must always be the possibility of further escape if the fire continues to grow. Where there is normally a need to maintain a secure perimeter to exclude outsiders, then it must still be possible for escape. After many disasters in previous years the era of bars on windows trapping people and locked doors preventing escape should be over, but the advent of pass or password controlled doors will lead to fatalities unless there are simple and effective overrides, both at the doors themselves and generally once a fire is detected or the alarm raised. 4.1.4 Familiarity If the occupants are familiar with the building, they will obviously find less difficulty in escaping from fire than those unfamiliar with their surroundings. In a strange building people will instinctively try to escape the way they came in, and it may be hard to persuade them to escape via “official” designated escape routes if these are in the opposite direction. Therefore normal circulation and exit routes should be used as escape routes. Escape routes which are not normally used, and only available in an emergency, should be avoided if at all

50

Occupancy

possible. If they are unavoidable, perhaps in a venue where ticket checks are essential as people enter slowly (e.g. concert halls) but this would be too slow for escape, then they will require explicit signposting. Familiarity will vary with building type. In a normal domestic situation the occupants will be very familiar with the layout of their own house or flat. Similarly, offices and factories which have a stable workforce that is familiar with the access and exit routes. Problems occur however, in places like hotels and hostels where the residents may only stay one night. Possibly most dangerous of all are complex buildings where large numbers of people are in a highly controlled environment with many areas normally prohibited to the general public, such as airports and shopping centres. In the fire at the Summerland leisure complex the high death toll (50 of the 3000 in the building) was, in part, due to the complexity of the building and the unfamiliarity of the occupants. It had seven levels, built against a cliff face with the main entrance on level four. The building had been conceived as the solution to the British summer, creating a Cornish village with a Mediterranean climate. By the time it opened in 1972, it had become more of a fun palace with bingo, disc-jockeys, amusement arcades and a variety of licensed bars. The Committee of Inquiry concluded that the high loss of life was due to rapid fire spread, delays in evacuation due to management faults, lack of escape stairs, the locking of exit doors and the confusion as parents and children in different parts of the building tried to find one another. Evacuation was hampered by the wrong response and by the lack of familiarity with the building’s layout, some vertical escape stairs not being used by the occupants because they did not realise they were there. 4.1.5 Response The likely response to a fire or a fire alarm has to be considered as another feature. When a fire occurs or an alarm sounds, a variety of actions may take place. In a building where the staff are well trained, with a planned evacuation strategy, the response should be markedly different from buildings which contain people who may be unwilling or unable to appreciate the danger. In this context, an office building or an acute/surgical hospital may be safer buildings, while a dwelling which is otherwise completely familiar may conceal hazards. In high ignition or fuel hazard premises there may also be the problem of isolated staff who could be unaware of a developing fire. There have been various studies of human response to a fire or fire alarm, which show that people do not react immediately. Instead they make contact with others in search for further information, they may make the wrong assessment of the situation or they may just ignore the alarm. Studies of past fires do not confirm the popular misconception that people panic. Rather people react wrongly, because of poor information or poor understanding of the building or the fire. Where people are given clear instructions or can understand the strategy, then they will follow them.

51

Escape

The inclusion of a fire alarm and detection system can be critical in ensuring an informed response and encouraging swift action. Training is also crucial in eliciting the right response from the staff or occupants. In the 1978 Taunton sleeper train fire there were survivors from sleeping compartments close to the source of the fire, while others who were further away died. Subsequent investigation showed that one of the survivors had some training in fire safety and used that knowledge to survive. She crawled along the corridor to the exit, but finding that locked then returned to her compartment, shut the door and waited on the floor until she heard the service enter before attempting again. 4.1.6 Occupancy and building type Table 4.2 offers designers, particularly student architects, general guidance on making an assessment of the critical factors discussed in the text related to building type. Some building types or some multi-use complexes mean that only a functional, holistic approach to fire safety will be appropriate. The table can therefore be used to establish a risk factor for any type of occupancy, or any mix of occupancy. It must be emphasised that this approach may not be endorsed by the enforcing authorities in some countries, but it does offer the designer some kind of rationale on which to develop a sensible fire safety design. The table shows that the building types posing the most severe risk are residential care buildings and hospitals, which show problems under three of the fire factors. In relative terms these are ones where escape may be very slow. Dwellings, other residential buildings, assembly and entertainment

Table 4.2 Building type and occupancy characteristics

Building Type

S

1 2 3 4 5 6 7 8 9 10

x

Dwelling Assembly and entertainment buildings Factory Office Open-sided car park Residential care building Hospital Residential building (other than residential care building or hospital) Shop Storage building (a) higher risk (b) lower risk

x = a problem in escape S = sleeping N = numbers M = mobility F = familiarity R = response

52

N

M

F

R x

x

x x

x x x x

x x x

x x x x x

x x

Travel distances

buildings, high-risk storage buildings and shops have problems under two headings and in relative terms escape can be described as slow. In relative terms factories, offices and low-risk storage buildings can perhaps be said to have “medium” escape speeds, while only open-sided car parks which have no particular problems could be described as having “quick” escape. The special problems associated with very tall buildings (over 20 storeys) or deep basements (more than one level) would of course, need special attention. 4.2 Travel distances Having considered the characteristics of the occupants which will influence escape and having seen how these can be related to building type, it is now necessary to consider the process of escape and the distances which people might be expected to be able to travel. Escape is best considered in four stages: Stage 1: escape from the room or area of fire origin. Stage 2: escape from the compartment of origin by the circulation route to a final exit, entry to a protected stair or to an adjoining compartment offering refuge. Stage 3: escape from the floor of origin. Stage 4: final escape at ground level. In a very simple layout the stages are illustrated in Figure 4.1. However, in more complex buildings where the evacuation is phased, stage 2 of the evacuation may only be to evacuate to a place of safety on the same level (a refuge). In high-rise buildings it may not be intended to commence total evacuation and there might be a desire for a phased evacuation. However, with almost everyone having mobile telephones, and being more aware of the dangers of being trapped since the Twin Towers disaster in New York, it is no longer credible to expect people to wait while a fire is growing below them. Phased evacuations only work in low and medium-rise buildings with a strong management structure (e.g. hospitals). They may involve stages 1 and 2, with stage 3 held in reserve, the total evacuation of some occupants (stages 1–4), while others are put on alert in readiness for evacuation if necessary. 4.2.1 Stage 1 (out of the room of origin) In achieving escape from a room the speed of the fire spread needs to be considered and compared with the speed with which the occupants can leave. However, it is extremely difficult to predict the rate of fire growth or fire spread, all that can be done is to ensure that the occupants of the room become aware of the fire as early as possible. In a large room it may also be necessary to provide more than one exit, so that occupants are never too far from a door and most importantly can move away from the fire towards the door, rather than having

53

Escape

4.1 Stages of escape

i

7

3

2.

C H W U fi PUN NING.

1* 2 .

OPCrN PLANNING

to move towards the fire to escape from the room. The maximum distance from the furthest part of the room to a door is referred to as the stage travel distance. It is sometimes necessary to plan an area so that access to one room is through another (Figure 4.2). It may be a requirement of a client that access to inner offices or secure areas is through an outer space, or in domestic accommodation that en suite bathrooms are entered through the bedroom. In fire safety terms such planning is defined by the terms “inner” and “access” rooms and the whole arrangement is treated as stage 1 of the escape. In this situation it is important that anyone in the inner room is not trapped by the development of a fire in the access room. This can be ensured by glazing in the separating wall or possibly if it is acceptable by stopping the separating wall before it reaches the ceiling. A sensitive communications system with detection in the access room and the alarm audible in the inner room should also normally be sufficient. It may also be sensible to manage the uses of the two rooms so that the inner room does not have too high a life risk and the access room too high a fuel load or ignition risk.

54

Travel distances

4.2 Inner room and access room / N N t-n AOOM .

ACCS-SS ROOM.

4.2.2 Stage 2 (out of the compartment of origin) The next stage of the escape is to leave the compartment or sub-compartment of origin where the fire ignited. This is usually by a circulation route which can lead to the outside or to a protected stairway or to an adjoining compartment which provides refuge. The occupants need to reach a place of safety away from the area affected by the fire, either by leaving the building entirely or by moving away from the fire protected by sufficient fire containment measures. In this context the fire containment may include sub-divisions of fire compartmentation termed “sub-compartments”. Compartments are often defined by their ability to give one hour’s protection from a standard test fire, while sub-compartments only provide 30 minutes protection from such a test fire. The designer should divide the building into compartments so that all the occupants will have sufficient time to be able to escape from the compartment of origin before being overcome by fire or smoke. However, as people, buildings and fires vary so much it is extremely difficult to calculate precise times. Therefore most codes and legislation specify distances derived from past fires and past “experience”. The most commonly quoted of these in the British Isles is twoand-a-half minutes and this has often been used as the basis for design guides and escape planning. However, its authority is tenuous and can be traced back to a real fire and a legend which grew up around the event. During a performance at the Empire Palace Theatre in Edinburgh (now the Festival Theatre) in 1911 a fire backstage killed 11, including the famous illusionist “The Great Lafayette” (Sigmund Neuburger) who was performing. The safety curtain was lowered, but was obstructed by items on the stage, so that the auditorium began to fill with smoke. However, the orchestra played “God Save the King”, at which the audience stood and then marched out (carrying the ladies who had fainted it was reported). No member of the audience was hurt and as it takes two-and-a-half minutes to play the national anthem, this became a design standard. Even if it was possible to establish reliable escape times, these would still have to be translated into escape distances with even more approximations

55

Escape

being necessary. The architect is therefore reliant on a difficult and complex modelling of the fire or working from first principles to make an assessment of the life risk and the feasible travel distances. Obviously it will be necessary to comply with the local and national legislation, but at the early design stages and for the coherence and integrity of the design it is important to get the principles at least approximately correct (see figure 4.3). Table 4.2 linked occupant characteristics to building type and this first principles approach can be developed to give rough guides to reasonable travel distance. These figures do not follow any particular code or approved document and are intended primarily for student architects working at the sketch design stage. The combined distances in Table 4.3 give a suggested overall distance. All occupants, wherever they are situated within the building, should not have to travel more than this distance to reach a place of at least temporary safety. These figures have been developed taking a maximum travel distance of 50 m for stages 1 and 2, and then reducing this by 10 m for each problem identified. Therefore a building with three of the five characteristics where it is assumed escape would be “very slow” would have a reduced travel distance of 20 m for stages 1 and 2. Buildings with two characteristics where escape would be “slow” have a combined distance of 30 m. Buildings with just one characteristic where escape would be “medium” have a distance of 40 m and buildings where escape might be expected to be relatively “quick” having the full 50 m. The initial figure of 50 m has been chosen as a conservative estimate of what an able-bodied adult can walk along an unobstructed corridor in one minute (see section 4.1.3). By selecting the distance to be travelled in a minute it is being stressed that ideally stages 1 and 2 should be completed within one minute of the occupants becoming aware of the fire, either by detection of it themselves or hearing the alarm. This figure of one minute is just as open to criticism as are all other estimates, and it is only offered as a very rough guide.

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4.3 Direct distance and travel distance

56

Travel distances

Table 4.3 Building type and travel distance

Building type

Travel distance (m) stages

1 2 3 4 5 6 7 8 9 10

Dwelling Assembly and entertainment buildings Factory Office Open-sided car park Residential care building Hospital Residential building (other than a residential care building or a hospital) Shop Storage building (a) higher risk (b) lower risk

1+2

stage 1 stage 2

30 30 40 40 50 20 20 30 30

15 15 20 20 25 10 10 15 15

15 15 20 20 25 10 10 15 15

30 40

15 20

15 20

The combined distances can be separated to provide travel distances for stage 1 (out of the room of origin) and stage 2 (out of the compartment of origin). The distance of stage 1 being taken as a maximum of half the total distance. Stage 1 escape will almost always be possible in only one direction and so the figure given for stage 1 is also the limit for single direction of travel. However once outside the room of origin, the designer must always provide alternative routes, so that the occupants can turn their backs on the fire and move away from it. Therefore the stage 2 distances are based on the assumption that there are alternative escape routes and the distance given is that to the nearer of the two exits (Figure 4.4). The figures in Table 4.3 provide a very rough guide and take no account of the concept of equivalency outlined in Chapter 1. It might well be that if alternative fire safety measures are included in the design, then the travel distances might be able to be increased. The special problems associated with very tall buildings (over 10 storeys) or deep basements (more than one level) would, of course, need special attention. Table 4.4 has been included to provide a rough guide, again primarily for the student architect working at the sketch design stage. They provide information on the number of exits which will be necessary from large spaces (e.g. concert halls, exhibition centres, etc). They should be used in conjunction with the travel distances in Table 4.3 and with the same caution. Escape routes must be wide enough and as a rough guide the aggregate unobstructed width (in mm) of all escape routes from a room or storey should be at least 5 or 6 times the occupancy capacity. In addition, each individual escape route should be at least 1200 mm wide (possibly reducing to 1000 mm where the routes are only accessible by steps and so there is less possibility of people using wheelchairs or with serious mobility problems using

57

Escape

4.4 One-way and twoway escape OH?-WAY 6SCAP&-.

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Number of people

Minimum number of exits

Not more than 60 61–600 601 or more

1 2 3

them). Escape routes may narrow at doorways if the occupancy capacity does not exceed around 200. The codes of practice for escape in residential care homes and hospitals, all recognise the importance of the concept of refuge. At its simplest this means that those who are ill, infirm, frail or unable to move easily move only the short distance to behind a compartment wall (see figure 4.5). There they can wait until either the fire is extinguished or if they are forced to move further there will be more staff and fire fighters to assist. In the case of people with impaired mobility in offices shops or other non-domestic buildings, protected refuge areas should be provided at the entry points to escape stairs and dedicated alarms can be provided to alert fire fighters that there are people requiring assistance in particular refuge points. A further refinement is to sub-divide compartments into sub-compartments so that as the occupants move away from the fire more walls with fire resisting construction are placed between them and the hazard (see figure 4.6). Movement from refuge to refuge building up more lines of protection between the occupants and the seat of the fire is sometimes called progressive horizontal evacuation. 4.2.4 Stage 3 (out of the floor of origin) Having escaped from the floor the fire originated, the occupants will need to escape down, or up, to the ground level, if they are not already there, and this vertical escape is stage 3. Even if the evacuation plan envisages refuge on the floor of origin the possibility of stage 3 will still have to be provided for, should the fire continue to grow unchecked.

58

Occupancy

4.5 Egress versus refuge

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The significant feature of stage 3 escape is that those escaping should already have achieved some protection from the fire by leaving the compartment of origin and that they should not have to re-enter any hazardous area on their route to the ground level. Where there are large numbers escaping from different floors it will be important that the staircases are wide enough to accommodate the increasing numbers entering at each floor. Staircases or ramps will normally be the only way of moving to the ground level. Lifts are generally dangerous in fire situations as the occupants might be trapped by a power failure or taken to a more dangerous floor by the lift being summoned. Even waiting for a lift is potentially dangerous as it delays escape. However, in some high rise hospitals specially designed lifts are installed

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59

Escape

which can be used to evacuate patients in their beds. These have an independent power supply, the potential for control from within the lift and communications between the lift and the emergency control centre. 4.2.5 Stage 4 (final escape at ground level) Stage 4 escape is from the foot of the staircase to the outside. Such escape should not involve the re-entry to possibly hazardous areas and different stairs should not all converge into one common area at ground level; otherwise a single incident can simultaneously block all routes. Although this might appear obvious, there have been numerous designs where safe routes from the upper storeys then discharge into a common central atrium or area. It should not be forgotten that the final exit and external design of a building also have to be considered in escape planning so that it is possible to get away from the perimeter of the building to a place of safety. Planning needs to take account of the volume of people that may escape from a building, and the need for a readily identifiable assembly point or transfer area. Where large numbers of people may be involved, it will be necessary to plan these areas, so there is no conflict of use as the emergency services arrive and begin to fight the fire. 4.3 Rescue Buildings divided into several fire compartments at each level, and with escape stairs positioned so that from no area is there only one direction of escape, should not have to rely on rescue by outsiders. However, many buildings (including most domestic dwellings) are single-staircase buildings, while others do not have any fire compartmentation or have inadequate standards of fire separation. In these situations the occupants may need to be rescued from windows or balconies. In designing to provide refuges for those who have disabilities or impaired mobility there is also the assumption that rescue will eventually be provided by some external group, whether by the fire service or by staff from elsewhere in the building. The fire services will always try to rescue the occupants using the staircases within the building, but as a last resort ladders or platforms might be necessary. Therefore there are two aspects to designing to make rescue easy, reaching the building and getting through the facade. In terms of access for low-rise housing, it might be sufficient for a pumping appliance to get within 45 m of the front door. With larger buildings, any rescue will be more limited and may only be possible by hydraulic platform, for this to be feasible there has to be good vehicular access to the face of the building (Figure 6.2). Getting through the facade means providing some windows which are large enough for a firefighter, with full equipment including breathing apparatus, to enter from the outside. This can sometimes cause problems with the security requirements of the building. In the Woolworth’s fire in Manchester, people were trapped behind barred windows from which escape was impossible. Window escape

60

Escape lighting

must always be regarded as an opportunity for rescue rather than as part of a planned escape route and balconies can serve as a much safer place to await rescue. In some situations balconies can also provide a better route into a flat to fight a fire, if using the front door might jeopardise escape from other flats which share the same normal access routes. 4.4 Escape lighting It many buildings it may be necessary to light escape routes so that they can continue to be used should a failure cause the failure of the usual lighting circuits, with the probable exception of low-rise housing. It is of paramount importance in assembly buildings, such as theatres, cinemas and dance halls. In one notorious incident the Six-Nine Discotheque in La Louviere, Belgium, 15 of the 60 people present lost their lives on New Year’s Eve 1975, when during a fire because of the lack of emergency lighting partygoers lit matches and lighters in order to see the exits. The club was decorated with flammable materials which were ignited thus making the fire far worse and leading to the fatalities. Escape lighting should be distinguished from the emergency lighting which might be installed to cope with a failure of the mains supply by using a standby generator. Such emergency lighting cannot be guaranteed to function in a fire as it probably uses the same circuits. Escape lighting will be provided by self-contained fittings which will function for a set period of time, usually three hours. These may be separate fittings or incorporated into the normal lighting units. If it is possible to install the escape lighting at low level, then this is even more useful as corridors and rooms will fill with smoke from the ceiling downwards, and lights below the smoke level are obviously more effective. Most people will be familiar with such escape route lighting as it has been required in passenger aircraft since an aircraft fire on a runway at Manchester Airport in 1985, where 54 passengers died partly because they could not find their way to the emergency exits due to the thick smoke. The designer should provide escape lighting for the circulation routes (stage 2), stairways (stage 3) and final exits (stage 4). Stage 1 escape, from the room of origin, will only require illumination if it is particularly large, there are likely to be significant numbers (50 or more), or the escape route is particularly tortuous (e.g. changing rooms). It is particularly important to light changes in direction routes and to indicate the location of any particular important equipment. In industrial buildings and in plant areas it may be appropriate to use photo-luminescent paint to denote escape routes and final exits. It could also be of use in large semi-outdoor stadia as a form of way marking that can be seen in dim conditions or at night.

61

Chapter 5

Containment

The ability of a building’s design to contain a fire once started is critical to the protection of the property, the lives of the occupants and the safety of the surrounding buildings and people. It is the fire safety tactic most clearly covered by legislation and also the one with which insurance companies are most concerned. Whether or not the fire is detected and the communications system alerts people and equipment to take countermeasures, the design of the building should be such that the fire is contained and the spread of the heat and smoke is limited. Fire containment is the “fail safe” tactic which the designer has provided even if all other measures are ineffectual. As such, it is the one most attractive to regulatory and legislative authorities and the one they are least happy to see involved in “trade-offs” or calculations of equivalency. Fire containment provides the opportunity of achieving both of the fire safety objectives: property protection and life safety. That is, property protection through the limitation of fire spread and fire resistance provided to the elements of structure, and life safety through the limitation of smoke spread and through the provision of places of refuge within the building to which the occupants can retreat. This concept of refuge, as already described in Chapter 4, is particularly important in large and complex buildings where escape is going to be hazardous and slow, and where there are people whose mobility is going restricted. Where the occupants are vulnerable or frail there is the added desire to avoid taking them outside. Hospital and residential care home design is now based upon the concept of progressive horizontal evacuation to places of refuge, evacuating patients or residents to the outside might cause more life loss than the fire they are seeking to avoid. In high-rise buildings the fire must be contained and eventually extinguished from within the building, because the fire might be below the occupants and the distance to the ground might be too great. As always, it is the heat which is most damaging to the structure and the smoke which is most dangerous for the occupants. Therefore it is necessary for containment measures to tackle both these hazards and limit the spread of both heat and smoke (Figure 5.1).

62

Passive measures: structural protection

5.1 Threats from heat and smoke

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Fire containment is not only about containing the fire products to a particular part of the building of origin; it also concerns the threats to and from adjoining buildings. There is a responsibility to prevent fire spreading to adjoining properties and starting a more serious and possibly general conflagration. In this instance, it is the heat which is most dangerous either through radiant heat or through the spread of burning particles carried by convection currents. Equally it is necessary to try and prevent fires which begin externally from spreading to the building under construction; here the concern is to ensure that external materials and finishes are not easily ignited by radiant heat or burning brands. It is possible to design both active and passive fire containment measures. Active measures are those which require some form of communication to occur by informing people or equipment of the presence of a fire and instructing them to take measures to contain its spread. Most active measures of containment are concerned with the control of some spread and rely on the detection of the fire triggering some form of counter measure. These will be considered in the fourth and final section of this chapter. The most common active fire safety measures are probably sprinklers and other forms of auto-suppression, but as they are concerned with extinguishment as well as containment they will be considered in the next chapter. Passive measures of fire containment concern the nature of the building structure, sub-division and envelope. They will last the life of the building and will always be available as a defence against fire spread. Such passive measures can be considered under three headings, as follows: 1.

2.

Structural protection – the protection against the effects of heat provided to the structural elements of the building (columns, loadbearing walls and floors). Compartmentation – the division of the building into different areas and the resistance to fire and smoke offered to such subdivision (internal walls, doors and floors).

63

Containment

3.

Envelope protection – the protection offered by the envelope of the building to both the surrounding properties and people, from a fire within the building, and the building itself and its occupants, from a fire in an adjoining property (external walls and roofs).

These are shown in Figure 5.2 and will now be considered in the first three sections of this chapter. 5.1 Passive measures: structural protection 5.1.1 Protection of structural elements The level of fire protection which it is appropriate to give to the structural elements will depend upon the need for escape and extinguishment. First, how long will escape from the building take, and does the safety of the occupants depend on the provision of places of refuge inside the building? Second, is it necessary for firefighters to be able to work safely in the building, and is it necessary that the structure survives, so that the building can be rebuilt after a fire? If the building has only to survive until all the occupants have been evacuated then the necessary structural protection might only have to last a short time. However, if the life safety strategy relies on the provision of places of refuge within the building, or it is necessary for firefighters to be able work safely within the building, then protection requirements might rise. It might also be important to the building’s insurers that repair rather than rebuilding is possible, and this might lead to even higher standards of fire resistance and more protection to the structure.

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5.2 Passive fire containment

Passive measures: structural protection

Fire tests of materials, components and assemblies will give specifications in terms of minutes. However, it is very important to understand that when a material or construction is said to have a certain period of fire resistance, whether this is 30, 60 or 120 minutes, that does not mean that it will always last for 30, 60 or 120 minutes in a real fire. The periods of fire resistance are quoted for standard tests and it is very unlikely that every fire will exactly replicate the performance of the test. Each fire is inevitably different, with different rates of heat increase, different types of radiant heat, different levels of convection, different air and smoke and pressures etc. Therefore it is always a mistake to assume that an element or product with a given period of fire resistance will function for that period, it may actually last longer or it may last less. All that can be reliably assumed from the specified fire resistance time periods is that products with longer specifications will perform for longer than those with shorter specifications in the same fire conditions. This is often not properly understood by designers, or the statutory authorities, who can assume that a 30-minute fire resistant structure means they have a full 30 minutes in order to evacuate the building. Construction on site is also very different from that found in test rigs. Obviously, test samples are of the highest quality and workmanship; these standards will rarely be repeated on site. Test samples are also new, and it is important that the fire resistance of the assemblies in place is not jeopardised by the effects of mechanical damage, weathering or thermal movement. The designer must be aware of what is likely to happen over the life of the building and make allowance for this at the design stage. However, once the limitations of fire resistance specifications are understood it is possible to use them to determine what standards of performance should be set for different elements of structure in different situations. The amount of fire resistance which must be provided will depend upon the fuel load of the building. To provide a very rough guide the building types can be used as in Table 5.1. Although each project should be assessed separately as part of a full safety engineering process, Table 5.2 provides a crude guide of suggested periods of fire resistance (in minutes). This is derived from the first principles approach in Table 5.1, rather than any particular code or approved document. Very high fuel loads are considered to need up to 120 minutes of fire resistance, depending on height. High fuel loads are considered to need fire resistance specifications of between 30 and 120 minutes depending on height. Medium fire loads are considered to need fire resistance specifications of 30 minutes, except above two storeys where 60 minutes is more appropriate. Buildings with a low fuel load only need fire resistance specifications of 30 minutes for two storeys, and nothing if single storey. Table 5.2 is intended primarily for student architects working at the sketch design stage. The figures offer a very rough guide and take no account of the concept of equivalency outlined in Chapter 1. The special risks associated

65

Containment

Table 5.1 Building type and fuel load

Building Type

Fuel load

1 Dwelling (a) houses (b) flats and maisonettes 2 Assembly and entertainment buildings 3 Factory (a) high fuel loads (oils, furniture, plastics) (b) medium fuel loads (garages, printing, textiles) (c) low fuel loads (metal working, electrical, cement) 4 Office 5 Open-sided car park 6 Residential care building 7 Hospital 8 Residential building (other than hospital or residential care) 9 Shop 10 Storage building (a) high fuel loads (b) medium fuel loads (c) low fuel loads

Low Medium High Very high High Medium Medium Low High High Medium Medium Very high High Medium

Table 5.2 Building type and structural fire resistance

Building Type

Structural fire resistance (minutes) Single storeys Two storeys Three or more storeys

1 Dwelling (a) houses 0 (b) flats and maisonettes 30 2 Assembly and entertainment buildings 30 3 Factory (a) high fuel loads (oils, furniture, 60 plastics) (b) medium fuel loads (garages, printing, 30 textiles) (c) low fuel loads (metal working, 30 electrical, cement) 4 Office 30 5 Open-sided car park 0 6 Residential care building 30 7 Hospital 30 8 Residential building (other than hospital or 30 residential care) 9 Shop 30 10 Storage building (a) high fuel loads 60 (b) medium fuel loads 30 (c) low fuel loads 30

66

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60 60 120

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60

120

30

60

30 30 60 60 30

60 60 120 120 60

30

60

120 60 30

120 120 60

Passive measures: structural protection

with very tall buildings (over 10 storeys) or deep basements (more than one level) would need special attention. Having established the specification of fire resistance for which the structure of the building must survive the effects of heat, it is possible to design the structural elements to provide this amount of safety. However, structural protection is only as good as the weakest point in the design, and it is essential that detailing of the junctions between structural elements is as good as the fire resistance of the elements themselves. An additional problem for the structural elements in a fire is that the progressive collapse of the building can increase the loading which they have to carry. If the basement is intended to survive, then in designing the required level of fire protection it is necessary to consider the additional loads that might be imposed upon the basement with the collapse of floors above (Figure 5.3). It is also important that in complex structures all critical components are given an equivalent level of fire protection. For example, in a single-storey steel framed building the failure of the roof may remove the necessary lateral bracing and the result may be consequent collapse of the main structure, even though the main structure is well protected against fire. 5.1.2 Fire resistance The ability of a structural element to continue to function when subjected to the effects of heat is defined as its fire resistance and this is normally measured in terms of time. It is the fire resistance of assemblies, not just components, which must be evaluated. Some of the problems of terminology and fire tests have already been discussed in Chapter 2, and fire resistance has been described and one of the essential terms with which architects must be familiar. The fire resistance of a component, or assembly of components, is measured by the ability to resist

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67

Containment

fire by retaining its loadbearing capacity integrity and insulating properties (Figure 5.4). The loadbearing capacity of the assembly is its dimensional stability. The integrity of the assembly is its ability to resist thermal shock and cracking, and to retain its adhesion and cohesion. The insulation offered by a material is related to its level of thermal conductivity. Fire resistance is normally defined under these three characteristics (stability, integrity and insulation) and given in minutes or hours of resistance in terms of specified standard tests. In the case of elements of structure, only stability and integrity are immediately essential: however if the element of structure is also acting to subdivide the building either horizontally (floors) or vertically (walls) to contain the fire, then the insulation is also important. The next five sections will consider the fire resistance of materials most commonly used by the architect. Some of these have an inherent fire resistance; with others the designer must take steps to improve their fire resistance in certain conditions: there are three principal methods of doing this. 1.

2. 3.

Oversizing – deliberately increasing the size of an assembly, so that part of it can be destroyed or weakened without affecting the structural performance of the remainder. Insulation – providing a layer of insulating materials around the assembly to protect it from the heat of the fire. Dissipation – ensuring the heat applied to the assembly is rapidly dissipated to other materials or to the air, so that the temperature of the assembly is not raised to a critical level.

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68

Passive measures: structural protection

is often described as “sacrificial timber”. The surface degradation of the wood is normally in the form of charring and flaming will only occur with temperatures at the surface in excess of 350°C and the presence of a pilot ignition source. As the outer surface of a timber member char, they tend to stay in place and the inner core remains relatively unaffected and can retain its stability and integrity (Figure 5.5). The rate of charring may vary from 0.5 mm min–1 (oak, teak) to 0.83 mm–1 (western red cedar), but a value of 0.67 mm–1 is a widely accepted estimate for structural species. This approximation applies both to solid members and laminates, though laminates may actually perform better as they will not be so prone to knots or other deformations of the timber. The use of flameretardant treatments will not normally slow the charring rate. It is of course possible to protect timber by the use of insulating materials, but as the choice of timber was probably made because the designer wishes it to be exposed, this is an unattractive option in new buildings. However, it may be necessary when improving the fire safety of existing timber structures to consider the cladding of timber elements with insulating materials. The great advantage of timber to the designer is that failure is predictable and will occur slowly, the great disadvantage is the dramatic increase in the cost of timber elements which have had to be deliberately oversized. 5.1.4 Steel Unprotected steelwork will loose approximately half of its strength in temperatures of 500–550°C and is therefore very vulnerable in a fire. As a result it is essential that steel structural assemblies are protected either by insulating materials or the dissipation of the heat on the steel. There are a variety of insulating materials for steelwork. Obviously other structural materials (e.g. brick or concrete) can be used, but this is a very expensive solution. The more common materials are insulating boards, sprayed ftO O fi JO /S TS . ftO O fi JO /S TS .

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69

Containment

coatings or intumescent paints. Insulating boards can be used to encase steel beams and columns; there are also available insulating sheet materials which can be used to protect whole walls. The technology of their use is well documented, but care must be taken in detailing all junctions to ensure that no areas of unprotected steelwork are exposed. The disadvantage for the designer is the added bulk which the encasement of steel means, and the care which must be taken to ensure to ensure proper construction. Sprayed coatings are normally of mineral fibre or vermiculite cement. Intumescent materials react to heat by expanding and forming an insulating layer. They can be applied to steelwork as sprays or paints and have the advantage of retaining the profile of the structural element. The disadvantages of intumescents lie in their more limited fire resistance specifications (normally up to 60 minutes, as opposed to 120 minutes for sprayed coatings and possibly even 240 minutes for boards), and in the susceptibility of the material to abrasion damage either during construction or during the life time of the building. Intumescents must also be applied over suitably cleaned and primed steel, and the thickness of the layer must be checked before a top sealer coat is applied (Figure 5.6). Dissipation of the heat away from the steel is a more exotic option, but it is possible to use water to cool hollow steel sections or flame shields to reduce heat gains. It is even possible to design the structure such that it is outside the building envelope and therefore protected from the risk of internal fires. However, these techniques are very expensive and require maintenance throughout the life of the building. 5.1.5 Concrete It is possible to achieve very high levels of fire resistance specifications with reinforced concrete, up to 240 minutes is quite easy. However, as reinforced IN S U L A T IO N . sre e-c s e c n o u /N s o u r-e o e y - e a i/io s . - IN T U m x e N T PA/NT.

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70

5.6 Protecting steelwork

Passive measures: structural protection

concrete depends for its tensile strength on the steel reinforcement, it is critical that in the design of the elements sufficient protection is provided to the steelwork. Simply increasing the concrete cover to the reinforcement does not necessarily give an increasing increase in fire resistance because of the tendency of concrete to break off (spall) under heat. This can reduce the cover and risk the reinforcement. Therefore it might be necessary to provide supplementary reinforcement to counteract this danger if the concrete cover is going to need to be greater than 40 mm. One of the critical issues in the fire resistance of concrete is the nature of the aggregate which has been used, certain aggregates being more resistant to spalling and having a lower thermal conductivity. The issue of thermal conductivity is particularly important when the assembly is also providing a sub-division and it is important to limit heat transfer. Also critical can be the use of permanent steel shuttering when it is necessary to design the concrete slabs to withstand the failure of the steel. 5.1.6 Brick Brickwork is generally a very good fire-resisting material; and it is quite possible to achieve periods of fire resistance specifications of up to 240 minutes, the stability of the material being due to the high temperatures to which it has already been subjected during manufacture. However, there may be problems with large panels (over 4 m) of brickwork due to differential expansion and movement. In these instances, the restraints being applied to the edges of the panels become critical (e.g. brick panels in concrete framed buildings). 5.1.7 Glass Normal glass has very little fire resistance, offering little insulation and being liable to lose its integrity and stability as it shatters under fire conditions. However, there are various types of glass now on the market which offer some degree of fire resistance. The familiar Georgian wired glass can solve the problems of stability and integrity by holding the glass in place for a short time, but this still does not offer any insulation and radiant heat will still pass through the material. Toughened glass is now available (e.g. Pyran from Schott, Pyroswiss from SaintGobain Glass) which can achieve the same integrity and stability of wired glass without the unattractive appearance of the wires, yet these also fail to provide any insulation. The one type of glass which does offer insulating properties is laminated glass (e.g. Pyrostop from Pilkingtons, Pyrobel from Glaverbel). These incorporate a completely translucent and transparent intumescent layer, which in the presence of heat expands to form an insulating barrier. The disadvantages of such laminated glass lie in its weight, cost and limitations on external use. Such glass must also be ordered pre-cut, as this is a factory rather than a site job. With all three types of glass (wired, toughened, laminated), the design is as important as the choice of glazing material and it is essential that the frame will survive as long as the glass. It is crucial that the architect considers the fire

71

Containment

Passive measures: compartmentation

resistance of the complete glazing assembly (frame, ironmongery etc) and not just the glazing material itself. 5.2 Passive measures: compartmentation The compartmentation of the building into a series of fire- and smoke-tight areas will contain fire spread and gain time, the fire being contained while the occupants have a chance to escape or to take refuge until it can be extinguished. Compartmentation also offers the chance of containing the fire to protect, at least, the rest of the property while the fire is extinguished. Therefore compartmentation is important both for life safety and property protection. The fire protection of elements of structure not only ensures the building does not collapse, but can also help to compartment the building. However, to achieve complete separation into different compartments it will also be necessary to protect some non-structural elements such as internal walls and doors. The fundamental principle for the designer to remember is that the integrity of the subdividing elements must be maintained and there can be no weak points or cavities, however small, which breach the fire and smoke barrier. Any services or ducts which have to pass through compartment walls or floors must be designed to provide an equal level of fire resistance. A major threat to the fire safety of a building can come from the later addition of services or ducts which are cut through dividing walls by sub-contractors unaware or uncaring that they are breaching critical fire barriers. Every small gap or imperfection has to be fire stopped. Any doors through compartment walls must not only match the fire resistance of the walls, but care must be taken to ensure they will close quickly and precisely in the event of a fire. The simple door wedge can pose a major threat to the fire safety of a building and the lives of those using it. And as with glazing it is important that not only the door has the necessary fire safety properties, but that this is true of the whole door assembly, including the frame ironmongery, glazing etc. The size of compartments and therefore the frequency of compartment walls has traditionally been limited by building regulations and codes of practice, but with the steady move towards functional requirements rather than simple prescriptive specifications, it is important for the designer to be able to understand the fundamental principles upon which compartmentation should be based (Figure 5.7). The number of compartments into which each storey should be divided depends on the number of people and the amount of fuel load on each level. This, in turn, depends on the function of the building, and many standards specify a maximum floor area or cubic capacity for a compartment by reference to the building function. Obviously, each storey should be divided into at least two compartments, so that horizontal escape from one to another is always a possibility for the occupants. The more combustible the contents of a building are likely to be and therefore the higher the fuel load, the smaller should be

72

Passive measures: compartmentation

5.7 Compartmentation of a building

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the size of the compartments. A warehouse with a high fuel load (e.g. holding paint) should obviously be divided into smaller compartments than one with a low fuel load (e.g. storing steel sections), yet many standards take no account of this.

73

Containment

It is common for every floor to be a compartment floor as it is fairly easy to achieve fire and smoke resistance in floor construction. However, if each is to be a separate compartment, then the architect must ensure that the exits from each floor to the vertical circulation shaft (for stair, lifts, escalators etc), are also given an equivalent level of fire and smoke resistance. Compartments do not necessarily have to be restricted to a single storey, and it might be that a compartment includes a staircase leading up to a gallery, or the balconies surrounding an atrium. The geometry is unimportant, provided that the integrity of the compartmentation boundaries in each dimension is maintained. The spacing of compartment walls may also be determined by the ability of the occupants to escape, the maximum acceptable travel distance may be the key factor which necessitates smaller compartments than would be required if the fuel load was the only factor. The use of the building and the potential fuel load may be such that it would only be necessary to have two compartments on each floor, but three may be necessary to ensure that none of the occupants is too far away from a compartment wall which would provide access to a place of relative safety. It is common to provide a medium fire and smoke resistance to compartment walls and floors and this is often a 60 minute-fire test specification. However, this might need to be raised where there are also structural elements requiring more protection. Where it is necessary to provide additional divisions simply to reduce the maximum travel distances, then these are sometimes referred to as sub-compartment walls. Then only a low fire and smoke resistance is often considered sufficient, perhaps a 30-minute fire test specification. Obviously if the sub-compartment walls are also structural elements then they might need to have a higher level of fire resistance – and then this provides an additional level of safety (Figure 5.8). In addition to dividing the building up into compartments based on fuel load, the architect may also have to consider the fire protection of the escape routes from the building and treat these as effectively additional compartments. The vertical shafts containing the stairs and lifts will need to be provided with fire and smoke resistance, and it may be necessary to isolate routes to these shafts at the upper levels or from these shafts at the ground level to the outside walls of the building. These are normally referred to as protected shafts and protected routes, and they need the same level of fire resistance as other compartments within the building, Once an occupant of the building enters a protected shaft or route, they must be able to reach an exit to the outside at ground level without encountering any further hazards. Although each project should be assessed separately as part of a full safety engineering process, a rough guide to the maximum sizes of compartments for different building types is provided in Table 5.3. This is derived from the first principles approach of considering the fuel load of different building types (Table 5.1) rather than any particular code or approved document. It is based on the principle for non-domestic buildings of a maximum size of 900 m2 (30m × 30m) for very high fuel load, 1600 m2 (40m × 40m) for high fuel

74

Passive measures: compartmentation

5.8 Compartments and sub-compartments

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loads and 2500 m2 (50 × 50m) for medium fuel loads. This is linked to the assumption that every floor will be a compartment floor. With domestic buildings, each dwelling (flat or house) must be a separate compartment. Table 5.3 is intended primarily for student architects working at the sketch design stage. These figures are a very rough guide and take no account of the concept of equivalency outlined in Chapter 1. The special risks associated with very tall buildings (over 10 storeys) or deep basements (more than one level) would need special attention. Many statutory guidance documents allow a doubling of the compartment size where sprinklers for property protection installed (see next chapter, section 6.2.1). This would appear to be a reasonable assumption and has a long and respectable history in design terms. Therefore this has also been included in Table 5.3. The exception is dwellings and buildings with a significant number of life risk factors, such as hospitals and residential care buildings (see section 4.1.6) high or very high life risk. If sprinklers are installed in such buildings it is

75

Containment

Table 5.3 Building type and compartment size

Building type

Size of compartment

1 Dwelling 2 Assembly and entertainment buildings 3 Factory (a) high fuel loads (oils, furniture, plastics) (b) medium fuel loads (garages, printing, textiles) (c) low fuel loads (metal working, electrical, cement) 4 Office 5 Open-sided car park 6 Residential care building 7 Hospital 8 Residential building (other than hospital or residential care) 9 Shop 10 Storage building (a) high fuel loads (b) medium fuel loads (c) low fuel loads

Each dwelling separate 1600 m2 * 900 m2 * 1600 m * 2500 m2 * 2500 m2 * No limit 1600 m2 1600 m2 2500 m2 * 2500 m2 * 900 m2 * 1600 m2 * 2500 m2 *

* = can be doubled if property protection sprinklers are installed.

more likely to be designed for swift suppression (see section 6.2.2) rather than property protection and so there is no allowance for doubling. The fire resistance of the major building materials from which compartment walls and floors are likely to be constructed has already been discussed in this chapter, but doors also require special consideration. All compartments are going to be breached by door openings and it is therefore critical that what is used to block these openings in the event of a fire achieves the same level of fire resistance as the rest of the wall. The term fire door is now so abused that its use without qualification is almost dangerous. The architect must know precisely the level of fire and smoke resistance offered by the full doorset, the frame and the ironmongery being as important as the door itself. How long it will function as a barrier to heat and smoke should be given in minutes against a standards test, and it is quite possible to obtain resistances in excess of 90 minutes, even with two leaves opening through 180°. However, it is always better if trying to obtain a performance of 60 minutes or more for this to be through two sets of doors each having half the required resistance, rather than a single set. There is always the danger of doors being left open, or having to be opened for escape, so a double set increases the safety factor by providing an “air lock”. The designer must obtain guidance on the type of frame and the appropriate ironmongery to obtain the desired fire resistance whether or not doorsets are being used. Doors will also need suitable devices to ensure they remain shut, or that they will close immediately in the event of a fire. There are many ways of achieving this, but the architect must be careful to ensure that the chosen method is suitable for the use of the building. It may also be necessary for the door to be available for escape, so care must be taken in the choice of locking devices.

76

Passive measures envelope protection

5.3 Passive measures envelope protection The third role of passive fire resistance is to limit the threat posed by a fire to adjoining properties and people outside the building, and to limit the possibility of ignition by a fire in an adjoining property. In this, it is the roof and the external walls that require the architect’s attention, the roof because of fire spread by convection currents and the external walls because of radiant heat. The roof can prove a danger because, once well alight, flaming particles (timbers, etc) might be carried upwards by the convection currents and pose a hazard if they land on other buildings; these are often described as “burning brands”. Standards exist for designing roof constructions to resist penetration and fire spread when subjected to flame and radiant heat. However, there are no tests concerned with limiting the ability of the roof to burn to produce burning brands. It is possible to design your building to resist the threat from others, but harder to design your building to prevent it posing a threat (Figures 5.9 and 5.10).

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81

Containment

5.4.2 Venting The simplest way of stopping smoke spreading within a building is to allow the smoke to escape to the outside. While this will not extinguish a fire, it can contain the smoke to its area of origin and gain time for people to escape and for measures to extinguish the fire to be initiated. In a single-storey building this can most easily be done through roof vents, but it is also possible to design ventilation systems for multi-storey buildings using mechanical and/o, natural ventilation. The first essential for the designer to understand is the different zones which will develop within the smoke (Figure 5.13). The hot smoky gases from the fire will form the upper stratified layer below the ceiling (Zone A). They will float on the colder smoke-free air below (Zone B). The plume of smoke ascending from the fire entrains air as it rises and creates the upper layer. This stratification or layering of smoke is due entirely to the buoyancy of smoke being produced and, should the smoke cool, then the stratification will break down. Smoke production will increase exponentially with the growth of the fire. Although it may be possible to assume that initially the smoke will be able to exit directly through the vents in the roof, as the fire grows a layer of smoke will build up beneath the ceiling. The layer of smoke will get thicker as the fire grows, and the smoke level will consequently gradually descend. The increasing depth of the smoke layer will increase the pressure on the vents that JM O /ftV&NT/NG.

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5.13 Ventilation

Active measures

are available, expelling more air and reducing the capability for the plume to entrain more air, reducing the volume of smoke produced. The venting system needs to be designed to ensure that the smoke being added to the smoke layer is exactly balanced by that being released through the vents, so that the depth of the smoke layer remains constant and never descends to a height where it endangers the occupants who may well be trying to escape beneath it. The minimum requirement will be 2.5 m of clear height below the smoke level. Limitation of the sideways spread of smoke can be achieved by the installation of “smoke curtains”, barriers which come down from the ceiling and create “smoke reservoirs”. Such smoke curtains might be permanently in place or be triggered to descend by the detection of a fire. Smoke reservoirs are desirable because they limit the area of damage caused by the hot, smoky gases, and ensure that the vents can operate to their maximum efficiency (Figure 5.14). The screens which are used to contain the smoke should ideally be as fire resistant as the roof structure itself. The use of different depths of screens in different directions can ensure that if smoke production is too great for the capacity of the reservoir, then the spill over will occur into a less rather than more dangerous area (Figure 5.15).

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83

Containment

Smoke reservoirs need not necessarily be formed by the downstand of the curtains. They can equally well be formed by upstand areas into which the smoke can flow. The high vaulted roofs of a design can often be utilised in this way, so that smoke is contained above head height until it can be expelled from the building (Figure 5.16). It is quite possible to design the size of smoke reservoirs and the capacity of the ventilation system to ensure that the smoke level does not descend below a dangerous level. This would not normally be the responsibility of the architect, but it is essential that the architect in designing the ceiling and roof geometry fully understands the principles which must underlie such a design. The first stage is to estimate the fire size and it is important to understand the assumptions which have been made about the size of the fire likely to occur. Sprinkler systems are normally designed to limit the fire to a 9 m2 area, with a consequent perimeter of around 12 m. In retail premises this would lead to a fire of around 5 MW, assuming a fuel load of around 0.5 MW/m2. However, if fast response heads are used on the sprinklers this may halve the fire spread to about 5 m2 and the consequent potential fire to 2.5 MW. In calculating fires in sprinklered retail buildings these are often taken as the range of fires with which the design must cope, though obviously the nature of the retail space could significantly alter these estimates. The same figures could be used in other sprinklered buildings for design purposes, but care should always be taken to consider the specific nature of the fuel load and ignition risk. In unsprinklered buildings, where combustible material is arranged in stacks with aisles or spaces between them, then the fire size will be taken as the largest of these stacks. In other unsprinklered premises the estimation of the fire size becomes much more difficult and an estimate must be made based on fuel load and disposition. Having made a reasonable assumption on the design fire size, the architects will need to consider how low the smoke level can be safely allowed to descend. This will normally be at least 2.5 m above the floor level, so that escape

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5.16 Use of upstands

Active measures

routes are not jeopardised. However, if it is a multi-level space with balconies or mezzanine levels the safe minimum unobscured height might be significantly higher. Once the height of the base of the smoke layer is established, then the size of the available smoke reservoir can be calculated from the geometry of the ceiling and roof design. This must be large enough to store the smoke produced until it can be extracted. Smoke reservoirs cannot be too large because of the dangers of smoke cooling and losing buoyancy. Therefore the limiting size on smoke reservoirs is the plan area, which gives the amount of air in contact with the cooler air below. For high-risk buildings (e.g. shopping centres) the maximum reservoir size should not exceed 1000 m3, and for low-risk buildings (e.g. sports halls) no more than double this. These figures are provided as a crude guide for architects, especially students; the detailed sizing of the smoke extraction system is a matter for specialists. The architects need to be aware of the relative advantages and disadvantages of mechanical and natural ventilation in different situations (Figure 5.17). Mechanical ventilation must be designed with reliability in mind, so that it can be maintained, and when necessary repaired, throughout the life of the building. Natural ventilation is totally responsive to the ambient conditions and the external weather may well determine its effectiveness in the vent of activation. If the vent is on a flat roof then the effect of wind blowing across it might be to create a suction effect which would improve the effectiveness of the vent. However, if the vents are on a flat roof, and particularly a steeply pitched one, then those on the windward side might not function or be counterproductive. Therefore the design of the vents has to take account of these risks and any decision on natural ventilation has to consider the topography of the site, surrounding buildings, potential for new buildings which might be constructed and the prevailing winds.

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85

Containment

Another principal which the designer must not forget is the provision of inlet air to replace the smoke which it is intended to ventilate. Without the provision for replacement air to be drawn into the building, then the system will fail and no smoke will be ventilated. It is preferable when designing these inlets that they are widely distributed over the building, so that it does not matter where the fire occurs. The use of the doors as inlets may be possible, but provision might have to be made to ensure that the doors open automatically in the event of a fire and stay open. The same issues about mechanical and natural ventilation apply equally to the replacement air as to the smoke which it is intended will be ventilated. At some level within a building filling with smoke there will be what is called the neutral plane (Figure 5.18). The inlet air will be drawn in below this, because the pressure within the building is lower than that outside, while the air pressure above this plane is higher and the smoke will be forced out through the vents. It is important in the design of the smoke venting system that this neutral plane is high enough to limit smoke spread within the building. In a building with a sophisticated air-conditioning system, it is essential that attention is paid to the potential impact of the system on the smoke generated by a fire. If well designed, the system could be used to vent smoke from part of the building and to supply the necessary balancing inlet air. However this is far from easy to design and control, and in most fire situations the air-conditioning plant is normally designed simply to shut down or is set simply to extract air. Badly designed systems can spread the fire very quickly and there have been recent examples, especially in hotels, where a system has contributed to the very rapid spread of smoke throughout the building. Whatever use is made of the air-conditioning system, it is essential that provision is made for

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86

Active measures

easy access to override controls at an entrance to the building so that firefighters arriving can take control of the operation of the air-conditioning plant. The relationship between smoke ventilation and the operation of the sprinklers is a complex one and the architect needs to understand the principles. The provision of sprinklers should reduce the risk of fire growing beyond certain limits and these limits can be used as the basis for the estimation of likely fire size and the consequent design of the smoke ventilation system. However, the water spray from the sprinklers might cause mixing of the smoke layer with the clear air below and bring down the smoke level. The sprinklers might also cause a cooling of the smoke, which will reduce the rate at which it is expelled through the vents. These possible dangers of cooling and mixing can be counteracted by increasing the smoke vent size to ensure the smoke level does not drop, and thus the smoke will still be vented even if the temperature is slightly reduced (Figure 5.19). It is essential in buildings with a high life risk (e.g. shopping centres) that the spinklers and smoke ventilation are designed as an integral whole and work together. Sprinklers should be designed in such buildings primarily for life safety more than property protection. All types of containment, whether of heat or smoke, and whether active or passive, only gain time. They provide the opportunity for the occupants to escape and for an attempt to be made to extinguish the fire. Fire extinguishment is the final tactic available to the designer and will be considered in Chapter 6.

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87

Chapter 6

Extinguishment

However effective containment is in limiting the spread of a fire, eventually the fire must be extinguished. In Chapter 1 the “triangle of fire” was described, and it was explained how the removal of any of the three elements (heat, fuel or oxygen) would terminate the chemical reaction, so extinguishing the fire. In the open a fire may be left to burn itself out (uses up all the fuel), but in a building, even after the occupants have escaped, the fire must be extinguished to prevent the eventual total destruction of the property. The most common extinguishing agents are water, foam, carbon dioxide and dry powder (Table 6.1). Water is the most obvious and works by cooling the fuel and so removing the heat. To a lesser extent, water will also act as a smothering agent, removing the oxygen. Unfortunately water is a very effective conductor of electricity and so cannot be used on electrical fires or ones where this is a potential hazard. Water will not mix with oil-based products and so cannot be used on many liquid fires. Foam works both by cooling and smothering and is excellent in extinguishing many liquid fires. Different formulations of foam are manufactured with different expansion rates, and high expansion foams are used in some special installations to completely fill an area or room. Lower expansion foams are used from hand-held extinguishers to provide a blanket covering over smaller fires. Carbon dioxide will smother a fire and is particularly good on electrical fires as it does not act as a conductor. A concentration of approximately 25–30 percent of carbon dioxide in air is necessary to extinguish a fire. Table 6.1 The suitability of extinguishing media for different fires

Water Foam Carbon dioxide Powder

88

Fires in solids

Electrical fires

Fires in liquids

Fires in gases

Excellent Good Poor Poor

No No Good Excellent

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No No Good Excellent

Manual fire-fighting

However, carbon dioxide is toxic and a concentration of 12 percent can be lethal, therefore it is best used in small bursts in well-ventilated spaces. It is also very effective inside sealed cabinets or items of equipment. If it is to be used to cover an entire room, then it is essential that everyone has left first. Dry powder works by suppressing the combustion reactions in the flame. There are a number of different formulations available, including sodium bicarbonate (baking soda). In the recent past halogenated hydrocarbons (halons) were used as extinguishing agents and these might still be encountered. They are very effective anti-catalysts and if supplied in the correct concentrations (around 3–6 percent in air) could extinguish a fire virtually instantaneously. The most commonly used are gases at room temperature but were stored in the extinguishers as liquids under pressure. They also had the benefit of being usable on any type of fire and once the gases have dispersed there is no additional damage from the extinguishing medium. Unfortunately halons have two very substantial drawbacks. First, the environmental damage they cause to the earth’s ozone layer, which led to them being banned in many countries during the 1990s. Second, the decomposition products formed as the gas is exposed to the flame are very toxic and a concentration of 10 percent in air can be lethal. Therefore large-scale systems could only ever be used in uninhabited areas. Even the use of manual extinguishers could be dangerous and at least one fatality occurred when one was used inside a military vehicle to extinguish a soldier’s uniform. The lack of ventilation led to a dangerous concentration and the individual died even though the burns alone would not have been fatal. There are three ways in which extinguishing agents can be used: by the occupants themselves with manual fire-fighting equipment, through autosuppression systems, and finally by the fire service on their arrival. 6.1 Manual fire-fighting There is always a dilemma with manual fire fighting equipment. If the fire is very small it can be useful to people who know how to use it and can therefore quickly stop a fire growing and in industrial premises 90 percent of all fires are extinguished with hand-held extinguishers. However, if the fire is larger or is growing fast then it is far more important for the occupants to leave and let the professionals tackle the blaze. There is never time in a real fire to learn how to use an extinguisher. So although certain buildings might be required to have manual fire-fighting equipment, this is not a significant safety measure and its presence might even constitute a hazard if it encourages staff to attempt to fight a fire rather than simply leaving the building. Equipment can be divided in to three categories: hand-held extinguishers, fire blankets and hose reels. In a domestic situation there is even less value in manual equipment and the only device probably worth having is a fire blanket. If there is anything that cannot be smothered or extinguished with a glass of water then it is safer to just leave the building.

89

Extinguishment

6.1.1 Hand-held equipment These are possibly not even worth installing in non-domestic premises, unless the staff are expertly trained in their use, otherwise they will only be of value to the fire service. They should not be required in dwellings, as trying to use them may delay escape for a few critical seconds. Where installed they will most commonly contain water, but carbon dioxide might be provided to deal with electrical fires. If there are particular industrial processes or materials then more specialised extinguishing media might be used. If provided, they should always be sited near the entrances to compartments, so that they are on escape routes and also available if entering an area to fight a fire. As most have a relatively short discharge time, normally less than two minutes, then training is essential for them to be used effectively. 6.1.2 Fire blankets The one manual fire-fighting device which is worth installing in dwellings is a fire blanket. They can be used to smother small fires, particularly in the kitchen, including fat fires which water would make worse. They can also be used for wrapping round someone whose clothes are alight. They used to be made of asbestos or leather, but now they are normally made from fibreglass. 6.1.3 Hosereels Hosereels can obviously contain a much larger fire, but they require even more training to operate and may encourage staff to stay inside a building to fight a fire at the risk of their own lives. Therefore, except in very special situations, where there will be large numbers of trained staff, they should not be installed and if installed they will only be used by the fire service. They are also expensive both to install and especially to test and maintain. Where there is an overwhelming case for their installation the locations should be chosen carefully. There is a practical limit of about 30 m to the length of a hosereel, and with a jet of perhaps 6 m. This means that they should be positioned so that no part of the floor is more than 36 m from the hosereel. It is also important that they are not taken through compartment doors, meaning that these have to be left open, breaching the integrity of the barrier. While the architect will want to design the hosereel housing such that they do not dominate the building, if too cleverly concealed they may not be noticed. Access for regular maintenance and testing will also be needed. 6.2 Auto-suppression Auto-suppression systems are those which are activated in the event of a fire without any action by the occupants. The most commonly installed form of auto-suppression is sprinkler protection, but other forms are available for special risks. 90

Auto-suppression

6.2.1 Sprinklers Water sprinklers have been used since the end of the nineteenth century and they are considered so effective in minimising property losses that insurance companies will give substantial discounts (up to 60 percent) on the premiums to building owners who have installed them. Sprinkler systems are designed to extinguish small fires and to contain growing fires until the fire service arrives. Most sprinkler heads are heat sensitive, operating at a fixed temperature. Normally this is around 68°C, but in certain situations it might be set at a higher level. It is always wise to design it so that it exceeds the highest anticipated temperature by about 30°C. Each head acts as its own heat detector and, unlike in many Hollywood films, only those where the set temperature is exceeded will operate and release water. The maximum area which can be covered by an individual head depends on the potential fuel load, but 9 m2 is normally taken for all but the most special risks in high hazard areas. This gives the maximum fire size already discussed for smoke calculations, and it is expected that the fire will be contained within this area (3 m × 3 m, giving a 12 m perimeter). If fast response sprinklers are used then the fire may be contained within a smaller area, perhaps half this size. Sprinklers will not be able to extinguish a fully developed fire as the operation of too many heads reduces the water pressure at each open head to such an extent that it would be insufficient to suppress or control the fire. The contribution of sprinklers to life safety is harder to quantify, and their value lies in the limitation of the fire while the occupants have an opportunity to escape. However, issues of the interaction of sprinklers and smoke ventilation mentioned at the end of Chapter 5, must be considered by the designers. The detailed design of a sprinkler system is certainly not the job for the architects; however, they should be aware of the different systems available. “Wet” systems are full of water at all times, while in “dry” systems the majority of the pipework inside the building is air-filled until it is triggered (thereby reducing the risk of freezing in cold weather). “Alternating” systems can be changed from “wet” operation (in the summer) to “dry” operation (in winter). “Re-cycling” or “re-setting” sprinklers are ones where the heads can be closed once the fire has been extinguished (minimising water damage). A “pre-action” system is one which is dry, but where water is allowed in on a signal from a fast response detector (usually smoke) in advance of the heads being triggered. Sprinkler heads do not always have to be ceiling mounted, they can be wall mounted, and in the case of aircraft hangers they have even been installed in the floor to spray the undersides of aircraft. In high bay warehouses it may be desirable to have sprinklers at different levels within the stacks as ceiling mounted sprinklers would be unable to reach the seat of many fires. The architect has to ensure that the sprinkler designers have precise information about the potential ignition risks and fuel loads in each compartment. They will also have to coordinate the sprinklers with other service installations and settle the positions of the main stop vales and, especially in rural areas, 91

Extinguishment

alternative water supplies. To ensure that sprinklers have an adequate water supply it is normal to provide two separate sources, one would normally be the ordinary water mains, but the other might need to be from storage tanks or a private reservoir. 6.2.2 Life safety sprinklers Normal sprinklers are not as responsive as either smoke or heat detectors. To counter this lack of sensitivity, life safety sprinklers have been developed, sometimes called fast response or residential. The greater sensitivity is achieved by improvements to the heat collecting arrangements and a reduction in the thermal lag of the system by using lighter components. Some life safety sprinklers can be as sensitive as heat detectors. 6.2.3 Other forms of auto-suppression The decision on the installation of more specialised forms of auto-suppression will depend on the ignition risks, the fuel loads and the nature of the property to be protected. It will also be influenced by the cost as some can be considerably more expensive. If a system is to be installed it will probably be to attract an insurance premium discount, and therefore the standards of the insurers will have to be met. In addition to standard sprinklers, water can also be used in other forms of auto-suppression. Water spray systems are designed to extinguish flammable liquid fires or cool tanks and are more applicable to industrial plant than in buildings. Drenchers or deluge systems are designed to protect the external face of a building or a compartment (walls, windows, roofs) from damage by fire in adjacent premises. These may be manually triggered or linked into the fire detection system. Drenchers can also be used to cool elements of structure (e.g. steel beams) and they are potentially useful as supplementary protection over openings in compartment walls. It is quite possible to use carbon dioxide in an auto-suppression system. It has the advantage of doing little damage to the contents of the compartment and of being usable in electrical fires. However, the toxicity limits its use to areas which are unoccupied, to the protection of individual items of plant or equipment. It might be possible to use it in areas where people occasionally go, provided there is sufficient warning of a discharge to enable the occupants to escape. A particular use might be to protect the store rooms of a museum or art gallery. Foam can be used to protect particular items of plant or, in the case of high-expansion foam, completely flooding a room. As foam will be fairly damaging to the contents, it is normally only used for heavy plant or machinery rooms. It is also possible to install auto-suppression systems using dry powder as the medium, but as with foam this is fairly damaging to the contents and is likely to be only used in very special situations.

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Fire service facilities and access

6.2.3 Equivalency of auto-suppression The decision on whether or not to include some form of auto-suppression system within the design may well be determined for the designer by the client’s insurance company. However, if the architects are adopting a fire safety engineering approach to the design, they will also wish to consider the additional safety offered by such systems and compare it with alternative methods of achieving equivalent safety, perhaps through greater compartmentation. In a fire safety engineering approach to a complex building a more detailed analysis of equivalency would be necessary, including the role of smoke ventilation, the communications and, most importantly, the ignition risks and fuel loads. This is an area of specialisation where the designers will probably use a fire safety consultant. However, the architects do need to be able to understand the concepts put forward by the consultants and ensure that they are satisfactorily integrated into the design of the building. 6.3 Fire service facilities and access 6.3.1 Facilities In tall buildings, where the fire must be tackled within, the fire services require safe “bridgeheads” from which they can work (Figure 6.1). These need to be linked by specially protected lifts which, in the event of a fire, are solely for the use of the fire service. Such lifts require two independent power supplies with fire protection to the cabling. They also need good communications with the ground and they must be fully under the control of the people within the lift.

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93

Extinguishment

As the basis of the bridgeheads, the fire services need access to rising mains. These are vertical pipes within the building with a fire service connection or booster pump at the lower end and outlets at different levels within the building. Dry risers are recommended for the fourth floor and above in all buildings. In considering the height of the building it is important to work from the fire service access level. Dry risers are kept empty of water and the fire service supply water to the inlet at the access level. They can then attack fires on the upper levels without having to lay hose up through the building. Wet risers are kept permanently charged with water and so permit the fire service to fight fires without having to pump water up from the access level. This can save significant amounts of time in larger buildings, and they are common in buildings of 20 storeys or above. In some tall buildings supplementary pumps may be required if the mains pressure is not sufficient to raise the water to the full height of the building. Outlets from risers need to be positioned so that a fire in any part of the floor can be tackled by hoses attached to the outlets. This means that normally no point should be more than about 45 m from an outlet (measured along a route suitable for a hose), perhaps extending to about 60 m if the building is provided with sprinklers. Certain plant-rooms or tank rooms may be provided with inlets to enable the fire service to flood them with foam from outside the building. In exceptionally tall buildings it might be necessary to designate and protect certain floors at regular intervals which become refuge floors to the assembly of firefighters before they move up to attempt to extinguish the fire. Any building where this is being considered, most definitely requires a fully fire-engineered solution which considers the interplay of all potential risks, hazards and precautions. 6.3.2 Access It is essential that fire service access is considered at the early stages of the design as it can have an influence on the location of the building on site. Vehicle access should be provided to at least one elevation of the building, the one with the principal entrance or from where it is planned fire-fighting and rescue operations will be attempted. In the case of larger buildings (e.g. those with any compartment greater than 900 m2 or with a perimeter in excess of 150 m) then vehicle access should be to every elevation. In addition, if wet or dry rising mains are provided, then provision must be made to bring pumps within easy reach of the access level inlet to the mains (around 18 m maximum) and within sight of the building. The same would apply to any outlets to specialist flooding systems. A fire safe design should therefore allow for a pumping appliance to draw up in this position and to have an adequate supply of water (i.e. hydrants) within a reasonable distance. The firefighters should not have to travel far into the building, before reaching the stairs, and if provided the fire-fighting lift. The roads must be large enough, including gates, to handle fire appliances and this will include necessary turning circles. If the building is so high,

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Fire service facilities and access

6.2 Access requirements for fire service vehicles

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probably four storeys or higher, that hydraulic platforms or turntable ladders are likely to be deployed for fire-fighting or rescue, then these requirements are even more stringent (Figure 6.2).

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Chapter 7

Assessment

Risk assessment is now a ubiquitous and an expected part of almost any business or commercial activity. It can be dressed up in complex methodologies and the wealth of jargon which is often used to protect the specialist knowledge of professionals who make their living from such assessments. However, assessment is fundamentally very simple and can in its principles be understood by the average educated lay person. Risk assessment at is heart is simply the identification of those hazards which might jeopardise a business or activity and the assessment to which they have been mitigated, or removed, by the precautions which have been put in place, so leaving just the residual risk. The assessment of the dangers from fire is simply just this and in its fundamentals no different from business or financial risk assessment. The first principles approach to building fire safety which underpins this book is just such an analytical process. In the first chapter the risk to those in, or close to, buildings, and the buildings themselves was considered. The tactics available to the architect to mitigate these hazards of life safety and property were identified as prevention, communications, escape, containment and extinguishment, and then these were individually considered in the next five chapters. There will always be a residual risk that remains within a completed building and perfect life safety and property protection is unachievable. The extent to which the residual risk is acceptable will depend on the standards set by the authorities in the jurisdiction where it is constructed and in the next three chapters these standards are discussed for the United Kingdom (Chapter 8), the United States (Chapter 9) and Hong Kong and mainland China (Chapter 10). In the case of a new building on a “greenfield” site, the legislation normally sets the acceptable level of safety for the designer and, although there are alternative methods of achieving such a level, this is a helpful yardstick to measure against. However, few projects are simply for a new building and do not involve some measure of renovation, upgrading, extension, alteration, adaptation or refurbishment of at least part of the site. In these cases the fire assessment of what exists and what is proposed becomes part of the responsibility of

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Assessment

the design team. Such fire assessments are now more complex, not only because of the difficulty of identifying accepted yardsticks of safety, but because the activities carried on within the building are no longer the expected ones of the design brief, but the actual ones of the building in use. Up-to-date fire assessments are now required of most buildings, apart from dwellings, and this has meant that building work might require work as a result of an assessment even where there was no other intention to improve the building. Increasingly fire assessments lead to improvement works on buildings where work would otherwise not be necessary. In these cases the buildings will definitely be in use and the assessment will have to take into account both design issues and, equally important, management issues. Over the last ten years the amount of material published on the principles of fire assessments has grown almost exponentially and there is almost a danger of too much over-detailed information which can begin to obscure the relatively simple basis to the methodology. An architect faced with undertaking an assessment or negotiating with a consultant who has prepared an assessment needs to be aware of the fundamental concepts which underlie all fire assessments and appreciate their significance. When dealing with the statutory authorities (fire service, building control etc) then the ability to work from first principles and query any unfounded assumptions or dubious reasoning becomes critical. In very large buildings the architect will have the backing of a specialist fire engineer, but in most medium-scale jobs or improvement programmes it may be necessary to argue the case in person. Before beginning any assessment it is essential to be clear about the terminology being used. In fire assessment the correct use of words and phrases is very important, and it is necessary to distinguish carefully between the different terms. The word ‘ assessment’ itself can be used interchangeably with ‘ appraisal’, but needs to be clearly distinguished from ‘ audit’. An assessment or appraisal is an estimate of the risks and precautions within a building and a competent analysis of how far this meets the relevant benchmarks or comparative standards. While an audit is a much shorter process where an existing assessment or appraisal is examined to check for accuracy in the estimation of the risks and the appropriateness and implementation of the precautions. Audits therefore need to be a regular event in the life of any building and they ensure that assessment or appraisal is updated regularly. Somewhat confusingly, the term “risk assessment” is often used to encapsulate the whole of the fire assessment process, when the risk aspect of the assessment is only actually one aspect and needs to be balanced by assessments of the precautions, and the degree to which the residual risk, once the precautions have been considered, satisfies the legislative or other benchmarks and yardsticks. Therefore in this chapter the term ‘fire assessment’ is preferred, as it is more accurate and encompassing. A fire assessment is normally in three parts: first, an estimate of the risk; second, an estimate of the precautions; and finally, consideration of the extent to which the precautions balance the risk and how the building compares

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Assessment

with any benchmarks or yardsticks (see Figure 7.1). These three parts will be considered in the first three sections of this chapter. If only the precautions are considered, or only the risks, then you do not have a complete assessment. The value of the assessment lies in the calculation of the extent to which the risks which have been identified are mitigated, or compensated for, by the precautions which have been estimated. The fire assessment must provide useable results and not simply be the listing of building characteristics: in simple terms it must tell you whether or not the building is acceptable. Section 4 of the chapter

Fire assessment

1 Fire risks

1.1

Hazards -

2 Fire precautions

1.2 Probability of occurrence

Potential ignition sources • design issues • management issues Combustible materials • design issues • management issues 1.3 Possible consequences

Prevention • design issues • management issues Communications • design issues • management issues Means of escape • design issues • management issues Containment • design issues • management issues Extinguishment • design issues • management issues

Life risk Property loss

3 Balances and benchmarks Equivalency ‘trade-offs’

Assessment against benchmarks

Relative assessments 7.1 Fire assessment

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Risks

is a simple generic fire assessment in six stages with a checklist of 27 components. The final section of the chapter discusses fire assessors and who is best placed to undertake fire assessments of existing public buildings. 7.1 Risks The first part of an assessment is the estimation of the fire risks within a building, and like any other risk assessment process has three, now fairly standardised stages. First, the fire hazards have to be identified; second, an estimate has to be made of the likelihood of these hazardous events occurring (i.e. their probability); and finally, the possible consequent life and property loss has to be considered. The fire risk part of the assessment therefore reflects both the likelihood that harm will occur and a measure of its severity. Hazards are sets of conditions in the operation of a product or system with the potential for initiating a fire. They include not only consideration of the combustible materials which might burn, but also the sources of potential ignition. However, it is not sufficient to just list the hazards found in a building; the assessor has to make a judgement about the likelihood of these hazardous events occurring. For example, a soft furnishings store in a building should always be identified as a hazard because of the combustibility of the materials involved; however, the risk posed by this store will depend on the probability of ignition (management, services etc). In some uses the risk will be very small because sensible storage procedures have been adopted, the staff have been trained in handling such materials, and there are no services passing through the store. In other buildings a store of similar size will constitute a major risk, because the staff are untrained, no one has responsibility for its management, and a major service duct passes through the store. It is the same hazard, but there are very different risks. The risks which may be identified can be related to either the design of a building, or to its management. Typical design issues would include surface finishes and electrical installations, while management issues might include work processes and staff training. Many risks will inevitably involve both design and management issues, as with the soft furnishings store. The third stage in the risk assessment process is the consideration of the threat to life and property. Here the consequences of ignition to people and property have to be considered. In the example of the soft furnishings store it can be seen that the risk will vary depending on what buildings it is in and where it is located. If it was in a hospital basement beneath a ward block, then the risk would be much greater than if it were in an isolated building on the far side of the car park. 7.2 Precautions Having assessed the risks the second part of the assessment is to examine the value of the fire precautions within the building. The existing precautions need

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Assessment

to be identified, and an estimate made of how far these will reduce the likelihood of ignition occurring and/or mitigating the consequences should ignition occur. Fire precautions can be grouped under the five fire safety tactics already covered in the previous chapters: prevention, communication, escape, containment and extinguishment. The precautions which may be identified can be related to either the design of a building or to its management. Typical design issues would include travel distances and auto-suppression. Management issues might include fire drills and the maintenance of fire-fighting systems. Some issues, such as the planning of a communications system, would combine both design and management issues. The level of detail in a fire assessment should be broadly proportionate to the risks involved. The purpose of an assessment is not to catalogue every trivial hazard and deficiency in precautions. It is also unfair to expect an assessor to anticipate hazards beyond the limits of current knowledge. The term often used is that the assessment should be “suitable and sufficient”. This means that while it must reflect what are the serious problems, it cannot be expected to ensure complete safety from fire, an ideal which it is impossible to obtain. 7.3 Balances and benchmarks Once all the risks and precautions have been identified and an estimate made of their value, it is possible to attempt the third part of the assessment. This is the consideration of the extent to which the specific risks have been reduced or mitigated. Have the identified risks been balanced by adequate precautions? This estimate can be put in one of two ways: 1. 2.

What level of risk remains? What level of precautions exist?

These two ways are of course “mirror images” of each other and represent the fire assessment of the building. Once the fire safety of the building has been measured in this way it needs to be put into context and this can either be a relative assessment of one building against another, or the absolute assessment of the building against a “benchmark”. Relative assessments are of interest to the owners of large estates (e.g. hospitals, universities, industrial complexes) who may need to determine the priorities for their improvement programmes. However, the latter are the more usual as the trend is for fire assessments to be required of all buildings to which the public have access, with the concomitant requirement that where an assessment reveals shortcomings then the building will be immediately improved to the required standard or benchmark. Rarely will there be only one option to bring a building up to the required standard. Normally there will be a number of alternatives which need to

100

Simple generic fire assessment

be investigated. Inevitably the building owner will want to achieve the required level with the minimum expenditure and hopefully with minimum detrimental effect on the architectural qualities of the building. Some assessment schemes have been designed to offer alternative strategies for improvement and so assist the designer in choosing the most “safety effective” solution. 7.4 Simple generic fire assessment Although it is not possible or appropriate to provide detailed fire-assessment documentation, as this must vary with building type, use and jurisdiction, this section does set out the generic elements within any such assessment in a staged form. This is in six stages and builds on the methodology set out earlier in this chapter, the first principles approach of this book, and the detail in the chapters on each of the fire safety tactics. 7.4.1 Risks The first stage has to be the identification of the potential causes of fire and the people at potential risk, in particular: Potential sources of ignition 1. 2. 3. 4.

natural phenomena (see 2.1.1) human carelessness (see 2.1.2) technological failure (see 2.1.3) deliberate fire-raising (see 2.1.4).

Potential fuel sources 5. building fabric (see 2.2.1) 6. building contents (see 2.2.2) Occupants 7. 8. 9. 10. 11.

sleeping risk (see 4.1.1) numbers (see 4.1.2) mobility (see 4.1.3) familiarity (see 4.1.4) response to alarm (see 4.1.5)

This identification process will involve obtaining relevant information about building, the processes and the occupants, including details of previous incidents (near misses as well as fires). It may be necessary to interview the management personnel and a physical inspection of buildings will certainly be needed. The potential ignition sources and fuel sources will enable the fire hazards to be

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Assessment

identified. These can then be considered in the light of measures already in place for their elimination or control. This will lead to a necessarily subjective, but evidence-based assessment of the risk 7.4.2 Precautions The second stage is to consider the physical fire protection measures in the building. In particular those concerned with: Communications 12. 13. 14. 15.

detection (see 3.1) comprehension/analysis (see 3.2) alarm (see 3.3) signs and fire notices (see 3.4)

Escape 16. 17. 18. 19. 20.

out of room of origin (see 4.2.1) out of compartment of origin (see 4.2.2) out of floor of origin (see 4.2.3) final escape at ground level (see 4.2.4) escape lighting (see 4.4)

Containment 21. 22. 23. 24.

structural protection (see 5.1.1) compartmentation (see 5.2) envelope protection (see 5.3) active measures, if any (see 5.4)

Extinguishment 25. manual fire-fighting (see 6.1) 26. auto-suppression, if any (see 6.2) 27. fire service facilities and access (see 6.3) This might involve discussions with management, but will mostly require an inspection of buildings and of the technical details behind the design which are hopefully recorded somewhere. This will lead to a necessarily subjective, but evidence-based assessment of the precautions. Taken together these first two stages will include an assessment of around 27 components, as numbered above, and these can be considered as a basic checklist for a simple generic fire assessment.

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Fire assessors

7.4.3 Balances and benchmarks Having made an assessment of the risks and precautions, it is then possible to determine if the residual risk is acceptable and within the statutory requirements. There will also need to be some thought about the efficacy of the arrangements for the management of fire safety. This will include discussions with relevant persons, examination of documents for testing, maintenance, training drills, examination of policies for nomination of fire wardens, liaison with fire services, routine inspections, record keeping etc. This will lead to a necessarily subjective, but evidence-based fire assessment and a reasoned decision as to whether this is both tolerable and compliant with the legal requirements. 7.4.4 Record The first three stages need to be recorded, along with the supporting evidence and reasoning. Not only is this good practice, but in many jurisdictions a legal requirement. This is so that the enforcing authorities, normally the fire authorities, can request to see and verify the assessment if they wish. 7.4.5 Action Fire assessment is of no value if it does not lead to action. Therefore if deficiencies have been revealed it is necessary to formulate a list of actions required to mitigate risks or improve precautions. Even if the fire assessment is tolerable, it may well still be possible to make minor improvements. If the action list is extensive then priorities may have to be set, and if the deficiencies as serious then limitations may have to be placed on the use of the building, or certain parts of the building, until the priority works have been completed. As with any action list it is important to set realistic timescales which take account of the funds which will be available for improvements and the time such improvements will take to implement. 7.4.6 Audit A fire assessment is only of value while it remains relevant. Therefore it is necessary to ensure that once the assessment has been undertaken and recorded, that it is audited at regular intervals, and every time a significant change occurs to the building, occupants or activities. The purpose of the audit is to determine if the assessment is still accurate, or if it needs to be redone to reflect the changes which have occurred. Details of some of the many guidance documents published by government and other reputable bodies are included in Chapter 8. 7.5 Fire assessors The requirement for most public buildings to have fire assessments of them undertaken to satisfy fire or licensing regulations means that owners, or to use

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Assessment

the terminology of many regulations, “the responsible person”, may wish to employ a fire assessor (see Chapter 8). This is unlikely to be a role that the design team or architects will wish to undertake, especially for buildings which they have not designed or in which they are undertaking remedial work, however they will certainly encounter individuals or companies offering this service and describing themselves variously as “risk assessors”, “fire assessors”, “fire risk assessors” or similar. As was stressed at the start of this chapter, assessment is fundamentally very simple and can in its principles be understood by the average educated lay person, therefore the “responsible person” may well be able to undertake the assessment themselves. They will have to do some reading or research, but there is a lot of appropriate guidance which can be accessed from the legislative websites. What they need to be able to do is carry out an assessment similar to that set out in generic form in the previous section. They will have to be able to correctly identify the potential causes of fire and consider the people at potential risk (7.4.1), evaluate precautions provided to protect people (7.4.2), and determine if the residual risk is acceptable considering the arrangements for the management of fire safety (7.4.3). Based on this fire assessment the “responsible person” will then want to: record the assessment in case the enforcing authority requires it (7.4.4), take any remedial actions which might be necessary (7.4.5), and ensure there are arrangements to audit the assessment on a regular basis (7.4.6). If the assessment is done by the “responsible person” themselves, it is more likely to be understood and acted upon. A common experience in the forensic examination of a fire scene, is to find that the owners have perfectly competent, and expensively procured fire assessments actually on the premises, which have clearly never been understood or used. Should it be determined to employ a fire assessor then it is essential that the person or company so employed, should be fully competent and experienced to undertake such work. It is also worth remembering that just employing a fire assessor does not relieve the “responsible person” of their obligation to ensure the adequacy of that assessment. Although a fire assessor does not have be a chartered fire engineer they should have relevant experience, not only of the legislation generally, but of its specific application to the type of building being assessed. In the United Kingdom it is probably worth ensuring that they can show compliance with the competency criteria set down by the Fire Risk Assessment Competency Council. Use of a third party certificated body can assist in this process. The council recommends the use of fire risk assessment companies or consultants who are third party certificated to appropriate schemes by Certification Bodies which have been accredited by the United Kingdom Accreditation Service to confirm they are inspecting correctly against “scheme” requirements. All schemes maintain a register which lists the individuals or companies that have been assessed to meet the requirements of the scheme. Fire assessment has to be undertaken, just like fire safety design, from a first principles approach. If this is done then it is not particularly difficult

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Fire assessors

or onerous. However, assessments will always remain subjective and should not be treated as more significant or precise than they can properly claim to be. Undue accuracy may give an entirely spurious authority to assessments and consequently should be avoided. The wide variety of legislative and licensing requirements which have made fire assessment such a common feature in building management have encouraged an assessment industry which needs to be treated with caution. While many individuals and corporate organisations are well qualified and highly experienced to undertake the work, there are others who have limited knowledge and experience and may well undertake assessments far beyond their actual competence. The Rosepark care home had received a “general risk and compliance assessment report” about a year before the fatal fire. This was lengthy (70 pages) and wide ranging, but a very superficial document. Although it did cover fire, this was only among many other issues (four out of the ten problems noted), worryingly these were not the significant issues and the assessment totally failed to identify the problems which were later to lead to such a high loss of life. Even if the fire assessment report does identify problems needing resolution, it is only useful if acted upon, and the frequency with which expensive externally produced reports are left virtually unopened in the building manager’s office has already been discussed. Fire assessments are important and useful; however they do not by themselves either save lives or protect property.

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Chapter 8

Information

This chapter and the next two are intended to guide both architects and the staff of statutory authorities to the information they may need in working from first principles. There is so much information available that there is a real danger that important issues can become lost in a plethora of insignificant and confusing detail. This chapter cannot summarise all this information, instead it should serve as a guide to that which is most important for those working within the United Kingdom. The following two chapters cover the legislative positions in the United States and China respectively. The next three sections of this chapter consider the legislation relevant to the different parts of the United Kingdom; England and Wales (section 8.1), Scotland (section 8.2) and Northern Ireland (section 8.3). The relationship between Acts and Regulations/Codes is examined and the application and authority of the various documents is outlined. The precise details of the legislation are not reproduced as designers must have their own copies of the Approved Documents, Technical Standards or Technical Booklets, but an attempt is made to explain the relevance and application of the different parts of the legislation. There is then a section (8.4) on legislation within the United Kingdom which has fire safety provisions within it. Some of this applies to all three jurisdictions, some applies to only Great Britain (England and Wales and Scotland) and some applies to specific geographical areas such as individual towns or cities. Much of the legislation refers directly to the British Standards, and these are introduced in the section 8.5. These documents occupy a curious position, almost akin to legislation in their authority, and it is essential for the designer to be aware of the most important standards and their different numbers and codes. This is followed by a section (8.6) which summarises all the other guidance available from research, government and trade bodies. This includes a review of other textbooks which are available. Finally a list of advice sources is also provided in section 8.7. Most of the legislation relating to fire safety within the United Kingdom has been enacted as a result of tragedies or particular fires. It has therefore

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developed in a piecemeal fashion with different sets of legislation referring to different building types, and distinguishing between new buildings and existing buildings. The process of refinement and replacement has given the law an almost geological quality with Act and Regulation superseding previous Act and Regulation sometimes completely, as in a consolidating Act, sometimes only partially. This incremental process has left some gaps and created some areas of overlap. It can also be very confusing and it is not always consistently logical. This is another reason why the designer must consider fire safety from principles and not from legislative compliance. Although the development of the legislation is probably only of passing interest to the designer, various books give a good historical perspective of fire safety law, notably Read and Morris, Third Edition, 1993, Aspects of Fire Precautions in Buildings. One of the problems for the architect is the sheer mass and complexity of the legislation which could apply; this section does not attempt to summarise the legislation only to describe the “patchwork quilt” of overlapping documentation so that the design team can see how the different pieces interrelate. Not all documents have the same status and it is important for the architect to be aware that many of those to which statutory authorities may demand slavish obedience are only advisory. Legal requirements can be categorised in order of their significance as: (a) Acts of Parliament (or Enactments)– these are the laws passed by Parliament, either of the United Kingdom at Westminster or for Scotland at Holyrood, which have to be obeyed; however, these very rarely contain technical details, and normally only set up procedures or empower government departments to make Regulations. (b) Regulations (or Statutory Instruments)– made by government departments under enabling Acts, these have the force of law; they used to contain technical information, but in recent years the actual Regulations have been given instead as functional requirements. (c) Approved Documents and Guides – these do not constitute the law; they are normally simply advisory documents which suggest one method of fulfilling the requirements of the regulations. It is important in any consideration of legislation to understand the differences between functional requirements, performance specifications and prescriptive standards. Functional regulations state what has be achieved, but do not specify how much has to be achieved or how it is to be achieved. As such they offer the greatest flexibility to the designer in terms of compliance and are the easiest to understand. Almost all English and Welsh regulations are now written in functional terms. For example, “fire and smoke are inhibited from spreading beyond the compartment of origin until any occupants have had the time to leave that compartment and any fire containment measures have been initiated”. Performance requirements state how much, or for how long something must perform and the more sophisticated of the approved documents and guides are written in

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such terms. This means the designer can still determine the details of the design and have a specification which they must achieve. For example, “the containment measures must provide a fire resistance specification of 60 minutes according to the standard specified tests”. Prescriptive standards used to form the basis of all regulations and are still useful on occasion, however they do not leave the designer any choice as they state precisely what must be done. For example, “the wall must be constructed of solid brickwork at least 100 mm thick”. United Kingdom legislation can be divided into two broad categories: that dealing with new buildings and that dealing with existing buildings. New buildings are primarily the responsibility of the building control departments of local authorities, while existing buildings are primarily the responsibility of the fire prevention departments of fire authorities. Therefore in each of the first three subsections, dealing respectively with England and Wales, Scotland and Northern Ireland there are two parts, the first covering new buildings and the second the standards applied to all buildings and to which existing buildings might have to be upgraded even if no work had otherwise been intended. 8.1 England and Wales 8.1.1 New build : Building Regulations The Building Act 1984 consolidated the law relating to building control for England and Wales, but it contains no design information as such. The Act empowers the Secretary of State to make Building Regulations for the purposes “of securing the health, welfare and convenience of persons in or about buildings and of others who may be affected by buildings”. Under this successive regulations have been issued. The Act also gives local authorities some detailed powers to deal with such matters as adequate drainage, building on filled ground and demolition. In addition, the Act gives local authorities the power (sections 24, 71 and 72) to demand the provision of means of escape in case of certain buildings after consultation with the fire authority if these are not adequately covered by the legislation on existing buildings. The current Building Regulations for England and Wales were made under the Building Act of 1984, and are known as the Building Regulations 2010, although Part B covering Fire Safety was last amended in 2013. There are five functional requirements which apply to virtually all new buildings as follows: B1: Means of warning and escape The building shall be designed and constructed so that there are appropriate provisions for the early warning of fire, and appropriate means of escape in the case of fire from the building to a place of safety outside the building capable of being safely and effectively used at all material times.

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B2 : Internal fire spread (linings) (1) To inhibit the spread of fire within the building, the internal linings shall: (a) adequately resist the spread of flame over their surfaces; and (b) have, if ignited, a rate of heat release or a rate of fire growth, which is reasonable in the circumstances. (2) In this paragraph “internal linings” mean the materials or products used in lining any partition, wall, ceiling or other internal structure. B3: Internal fire spread (structure) (1) The building shall be designed and constructed so that, in the event of fire, its stability will be maintained for a reasonable period. (2) A wall common to two or more buildings shall be designed and constructed so that it adequately resists the spread of fire between those buildings. For the purposes of this sub-paragraph a house in a terrace and a semi-detached house are each to be treated as a separate building. (3) Where reasonably necessary to inhibit the spread of fire within the building, measures shall be taken, to an extent appropriate to the size and intended use of the building, comprising either or both of the following: (a) sub-division of the building with fire resisting construction; (b) installation of suitable automatic fire suppression systems. (4) The building shall be designed and constructed so that the unseen spread of fire and smoke within concealed spaces in its structure and fabric is inhibited. B4: External fire spread (1) The external walls of the buildings shall adequately resist the spread of fire over the walls and from one building to another, having regard to the height, use and position of the building. (2) The roof of the building shall adequately resist the spread of fire over the roof and from one building to another, having regard to the use and position of the building. B5: Access and facilities for the fire service (1) The building shall be designed and constructed so as to provide reasonable facilities to assist firefighters in the protection of life. (2) Reasonable provision shall be made within the site of the building to enable fire appliances to gain access to the building. 109

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Each of the five functional requirements states that the building should have a level of safety, but this is “appropriate”, “adequate” or “reasonable”. The Building Regulations are supported by Approved Document B which supplements these functional standards by defining what is appropriate, adequate and reasonable for different buildings and situations. There are two versions of Approved Document B, one for dwelling houses and the other for all other buildings. They are entitled “The Building Regulations 2010”, but do incorporate the 2013 changes. Like all UK government documents they are available free online, as well as being published in hard copy. There is no obligation on the designer to follow the solutions outlined in the Approved Document and they are entitled to meet the relevant requirement in any other way which they can demonstrate offers an equivalent level of safety; however, virtually all architects and statutory authorities tend to treat the Approved Document as if it was legally binding and treat alternative fire safety solutions with great scepticism. The position of Approved Documents can be compared with that of the Highway Code, it is not an offence not to follow it, but should anything go wrong, this will be the standard which the courts would look to as representing reasonable practice. In reality few architects have been brave enough to venture out on their own and the Approved Document has become almost a prescriptive piece of legislation which is obediently followed in virtually all designs. The Building Regulations are administered by the local district councils. The architect can either to go to them for approval or, in theory, to an Approved Inspector employed by the architect. Approved Inspectors are increasing in number and work either individually, or as corporate bodies. They provide real competition to Local Authorities and dominate the private house building market where the National House Building Council is an Approved Inspector. The Approved Documents are structured under the five functional requirements with sections covering the major areas of importance: B1: Means of warning and escape Dwellinghouses section 1: Fire detection and alarm systems section 2: Means of escape Buildings other than dwelling houses section 1: Fire alarm and fire detection systems section 2: Means of escape from flats section 3: Design for horizontal escape from buildings other than flats section 4: Design for vertical escape section 5: General provisions B2: Internal fire spread (linings) Dwellinghouses section 3: Wall and ceiling linings 110

England and Wales

Buildings other than dwelling houses section 6: Wall and ceiling linings B3: Internal fire spread (structure) Dwellinghouses section 4: Loadbearing elements of structure section 5: Compartmentation section 6: Concealed spaces (cavities) section 7: Protection of openings and fire stopping Buildings other than dwelling houses section 7: Loadbearing elements of structure section 8: Compartmentation section 9: Concealed spaces (cavities) section 10: Protection of openings and fire stopping section 11: Special provisions for car parks and shopping centres B4: External fire spread Dwellinghouses section 8: Construction of external walls section 9: Space separation section 10: Roof coverings Buildings other than dwelling houses section 12: Construction of external walls section 13: Space separation section 14: Roof coverings B5: Access and facilities for the fire service Dwellinghouses section 11: Vehicle access Buildings other than dwelling houses section 15: Fire mains and hydrants section 16: Vehicle access section 17: Access to buildings for firefighting personnel section 18: Venting of heat and smoke from basements 8.1.2 Buildings in use: Fire Safety Order Existing buildings are covered by the Regulatory Reform (Fire Safety) Order 2005 made under the Regulatory Reform Act 2001, commonly called the Fire Safety Order. This came into force in October 2006 and replaced virtually all the previous fire safety requirements placed on existing buildings, significantly

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tidying up and simplifying arrangements. Fire Certification under the 1971 Fire Precautions Act ceased and existing certificates needed to be replaced by regular assessments. In this way the duty of care was significantly moved from the statutory authority to the “responsible person”. Fire risk assessments if conducted under the Fire Precautions (Places of Work) Regulations 1997, were still recognised provided they had been regularly reviewed, however to all intents and purposes the Fire Safety Order became the single legislative provision affecting existing buildings. The Fire Safety Order requires employers, owners, landlords or occupiers of businesses or other non-domestic premises to take responsibility for fire safety. It defines the “responsible person” and places on them the duty to: • • • • •

carry out and regularly review a fire risk assessment of the premises; tell staff about any risks which have been identified; put in place and maintain adequate and appropriate fire safety measures to remove and reduce the risk to life; plan for an emergency; and provide staff information, fire safety instructions and training.

Like the Building Regulations the requirements are functional, using the words “adequate” and “appropriate” and are accompanied by guidance which provides more detailed information and suggested methods of compliance. These fire safety risk assessment documents cover the following building types: • • • • • • • • • • •

offices and shops, 2006 factories and warehouses, 2006 sleeping accommodation, 2006 residential care premises, 2006 educational premises, 2006 places of assembly, two documents one covering up to 300 people, the other over 300, both 2006 healthcare premises, 2006 theatres, cinemas and similar premises, 2006 open air events and venues, 2007 animal premises and stables, 2007 transport premises and facilities, 2007

There are also some useful general guides: • • •

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Guide to means of escape for disabled people, 2007. “Do you have paying guests?”, 2008 (covering bed and breakfasts and similar small-scale businesses). Fire safety in purpose-built blocks of flats, 2011 (published by the Local Government Association).

Scotland

Each of the premises specific guides is structured in the same manner, with the first part consisting of guidance on fire risk assessment, and the second further guidance on various fire safety precautions: section 1—fire risks and preventative measures section 2—fire detection and warning systems section 3—firefighting equipment and facilities section 4—escape routes section 5—emergency escape lighting escape 6—signs and fire notices section 7—recording, planning, informing, instructing and training section 8—quality assurance of fire protection and installation It will be noticed that surprisingly more attention is paid to the minor issues, such as signs, than the fundamental structural issues of containment. Enforcement of the Fire Safety Order is by the local fire and rescue authority, who have the power to inspect risk assessments and require upgrading works. 8.2 Scotland 8.2.1 New build: Building (Scotland) Act 2003 This section should really have preceded that of England and Wales as Scotland was the first to develop national standards for fire safety in new buildings in the Building (Scotland) Act 1959. The legislation was fully revised and updated in the 2003 Act of the same name and now has the best integrated and comprehensive system of building standards in the United Kingdom. The Act gives Scottish Ministers the powers to make building regulations for “the purpose of securing the health, welfare and convenience of people in and around buildings and of all others who may be affected by buildings”. This obviously includes regulations for fire safety and section 2 of the regulations made under the Act, (Building (Scotland) Regulations, 2004 as amended), includes 15 requirements. These are the legal requirements which virtually all new buildings must be designed to achieve. Unlike the functional requirements for England and Wales which make use of the words “appropriate”, “adequate” or “reasonable”, the Scottish Building Standards deliberately use concepts and phrases which could be interpreted by the courts without the need for any additional documentation. They are therefore arguably closer to being performance specifications. Unsurprisingly they align closely with the first principles outlined in this book. Communications Every building must be designed and constructed in such a way that in the event of an outbreak of fire within the building, the occupants are alerted to the outbreak of fire (2.11).

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Escape Every building must be designed and constructed in such a way that in the event of an outbreak of fire within the building: •

•

the occupants, once alerted to the outbreak of fire, are provided with the opportunity to escape from the building, before being affected by fire or smoke (2.9); illumination is provided to assist escape (2.10).

Containment Every building must be designed and constructed in such a way that in the event of an outbreak of fire within the building: •

•

• • • • •

fire and smoke are inhibited from spreading beyond the compartment of origin until any occupants have had the time to leave that compartment and any fire containment measures have been initiated (2.1); the load-bearing capacity of the building will continue to function until all occupants have escaped, or been assisted to escape, from the building and any fire containment measures have been initiated (2.3); the unseen spread of fire and smoke within concealed spaces in its structure and fabric is inhibited (2.4); the development of the fire and smoke from the surfaces of walls and ceilings within the area of origin is inhibited (2.5); the spread of fire to neighbouring buildings is inhibited (2.6); or from an external source, the spread of fire on the external walls of the building is inhibited (2.7); fire growth will be inhibited by the operation of an automatic fire suppression system (2.15).

Every building must be designed and constructed in such a way that in the event of an outbreak of fire in a neighbouring building the spread of fire to the building is inhibited (2.8). Every building, which is divided into more than one area of different occupation, must be designed and constructed in such a way that in the event of an outbreak of fire within the building, fire and smoke are inhibited from spreading beyond the area of occupation where the fire originated (2.2). Extinguishment Every building must be:

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• • •

accessible to the fire and rescue service (2.12); provided with a water supply for use by the fire and rescue service (2.13); designed and constructed in such a way that facilities are provided to assist fire-fighting or rescue operations (section 2.14).

These are functional requirements and performance specifications setting out what the design must achieve and how the building must function. They are not prescriptive in restricting how such performance and functionality is to be achieved and the architect has the freedom to satisfy the requirements in any way they choose. However, as most architects and designers value guidance and assurance that what they propose will be satisfactory, a series of more detailed performance specifications and prescriptive standards are available to support the 15 standards. These are available in two Technical Handbooks, one covering domestic buildings and the other non-domestic buildings. These handbooks are regularly updated and available in printed form and online. A further functional requirement under consultation, and very likely to be introduced as 2.16, is the requirement for the provision of fire safety information on all new non-domestic buildings in a form which can be passed from owner to owner over the life of the building. It can then be used by the fire risk assessor and the regulator under the requirements for existing buildings in the Fire (Scotland) Act 2005. It will be enforceable, as it can be required as part of the acceptance process for the completion certificate submitted to the verifiers under the Scottish system at the end before occupation, and so a copy will be held by the verifier. Although the Technical Handbooks are not mandatory, following them can be used as evidence of compliance with the regulations. The handbooks explicitly state that “fire safety engineering can provide an alternative approach to fire safety . . . [and] . . . it may be the only practical way to achieve a satisfactory level of fire safety in some large and complex buildings”. In addition to the Technical Handbooks there are a number of other documents which have been given similar practical guidance status by Ministerial direction. Possibly most interesting of these is the document produced jointly with Historic Scotland in two parts, “Conversion of Traditional Buildings”, which are valuable when altering historic buildings. There had originally been the intention that British Standard 9999, “Code of practice for fire safety in the design, management and use of buildings” (2008), might also be given the same status, however this did not eventually prove possible. Unlike the English and Welsh system, in Scotland it is always necessary to design a building and gain a warrant for its construction, before work can begin on site. To gain a warrant the plans have to be verified as fulfilling the requirements of the functional standards in the regulations, either by following the guidance in the Technical Handbooks or by some other method. Warrants can be issued by verifiers appointed by Scottish Ministers and at the time of writing only local authorities have been appointed in this role. Once completed the

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architect or designer has to certify that it complies with the regulations and the warrant. This certificate is then accepted or rejected by the verifier. 8.2.2 Buildings in use: Fire (Scotland) Act 2005 The Fire Safety (Scotland) Regulations 2006, made under Part 3 of the Fire (Scotland) Act 2005, introduced a fire safety regime that applies to virtually all buildings to which the public have access (as well as houses in multiple occupation and domestic buildings where staff are employed). Fire assessments are required for such buildings and these can lead to the need for additional precautions such as improvements to reduce the risk and spread of fire or improve the means of escape, fire-fighting equipment, or fire detection and warning facilities. Specific guidance is published for ten building uses: • • • • • • • • • •

Places of Entertainment and Assembly, 2007 Healthcare Premises, 2008 Care Homes, revised 2008 Offices, Shops and Similar Premises, revised 2008 Factories and Storage Premises, revised 2008 Educational and Day Care for Children Premises, revised 2008 Medium and Large Premises Providing Sleeping Accommodation, revised 2008 Transport Premises, revised 2008 Small Bed and Breakfast and Self-Catering Premises, revised 2010 Small Premises Providing Sleeping Accommodation, revised 2010.

Much of the material in these specific guides has been derived from the Technical Handbooks and an attempt has been made to ensure that where a new building is built in accordance with the regulations and the warrant it will satisfy the fire assessment for all those issues coved by the building standards regulations. As in England and Wales, the requirements for existing buildings are enforced by the fire and rescue, in this case the national Scottish Fire Service, who has the power to inspect fire risk assessments and require upgrading works. 8.3 Northern Ireland 8.3.1 New build: building regulations Northern Ireland has always had its own building regulations, although they have tended to follow fairly closely those in England and Wales. They are made by the Department of Finance and Personnel under article 3 of the Building Regulations (NI) Order 1979. The most recent version are the Building Regulations (Northern Ireland) 2012, which includes five functional requirements for fire safety:

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Northern Ireland

Means of Escape Regulation 33 – A building shall be so designed and constructed that in the event of a fire there is: (a) where appropriate, adequate means of detection (b) adequate means of giving warning, and (c) adequate means of escape, which can be safely and effectively used at all material times. Internal spread – linings Regulation 34 – To inhibit the spread of fire within a building the internal linings shall: (a) offer adequate resistance to the spread of flame over their surfaces; and (b) where they are located in a circulation space have a low rate of heat release or slow rate of fire growth when ignited. Internal fire spread – structure Regulation 35 – (1) A building shall be so designed and constructed that in the event of a fire, its stability will be retained for a reasonable period. (2) A wall common to two or more buildings shall be so designed and constructed that it provides adequate resistance to the spread of fire between those buildings and for the purposes of this paragraph a dwellinghouse in a terrace and a semi-detached dwellinghouse shall be considered as a separate building. (3) To inhibit the spread of fire within it, a building shall be adequately sub-divided with fire resisting construction. (4) A building shall be so designed and constructed that the spread of fire (and in particular smoke) within concealed spaces in the structure and fabric is adequately inhibited. External fire spread Regulation 36 – The external walls and roof of a building shall be so designed and constructed that they afford adequate resistance to the spread of fire over them, and from one building to another, having regard to: (a) in the case of an external wall – the use, position and height of the building; and (b) in the case of a roof – the use and position of the building.

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Facilities and access for the Fire and Rescue Service Regulation 37 – (1) A building shall be designed and constructed with such reasonable facilities as are necessary to assist the Fire and Rescue Service in ensuring the safety of people in and about the building in the event of a fire. (2) Reasonable provisions shall be made within the boundary of the premises for access to the building by fire and rescue appliances for the purposes of paragraph (1). Guidance on compliance with the regulations is provided in a series of Technical Booklets, the one on fire safety is Technical Booklet E, last updated in 2012. This is very similar to Approved Document B to the English and Welsh Building Regulations and approximately 80 percent of it is identical. This has the following sections: section 2 – Means of escape section 3 – Internal fire spread – Lining section 3 – Internal fire spread – Structure section 4 – External fire spread section 5 – Facilities and access for the Fire and Rescue Service section 6 – Common provisions Adherence to the methods and standards detailed in the Technical Booklet will be deemed to satisfy and must be accepted as compliant by the 26 local District Councils, who are the sole administrators of the building control system. 8.3.2 Buildings in use: existing buildings Existing buildings are covered by Part 3 of the Fire and Rescue Services (Northern Ireland) Order, 2006 and the Fire Safety Regulations (Northern Ireland), 2010. These require the appropriate person to take responsibility for ensuring that non-domestic premises reach the required fire safety standards. As such it is very similar to the requirements in England and Wales and in Scotland. The emphasis is on the carrying out of a fire risk assessment and then undertaking any improvements which might be needed. Guidance is produced on undertaking the fire risk in Northern Ireland, but for guidance on specific types of premises reference is simply made to the guidance published for England and Wales. As in other parts of the United Kingdom the requirements for existing buildings are enforced by the fire and rescue, in this case the Northern Ireland Fire Service, who has the power to inspect fire risk assessments and require upgrading works.

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Other UK legislation

8.4 Other UK legislation 8.4.1 Health and safety The Health and Safety at Work etc Act 1974, which applies throughout Great Britain, placed responsibility on employers, employees and others who may be affected by their actions, for health, safety and welfare. Under this Act a series of regulations have been introduced over the years which have provided detailed requirements and introduced into British law certain European directives on health and safety. The Act and its associated regulations are enforced by the Health and Safety Executive, which has a staff of well-trained and experienced inspectors. Section 2 of the Health and Safety at Work etc Act had placed a duty of care on the employer towards the employees in respect of safety. The employer must provide information, training and supervision and also maintain the place of work as safe, and provide means of access and egress that are safe. The employer is required to have a published safety policy and consult with safety representatives from the employees. Section 7 of the Act had placed a duty of care on employees for their own safety. In the Regulations there is a specific requirement to undertake risk assessments (regulation 3). There is also a requirement (regulation 7) to establish procedures for serious and imminent danger and danger areas, with fire being explicitly mentioned as one such danger. While it is unlikely that the Health and Safety Executive would wish to become involved in specifying general building fire safety, as opposed to the safety of particular work processes, it is a potentially overlapping area, particularly in premises such as care homes where there is a risk to the residents as well as to the employees. Designers will need to ensure that all statutory bodies make clear the reasons why they wish to become involved in a project, and clarify the precise regulations under which they are working. The Construction (Design and Management) Regulations 2007 are one particular covered by the Health and Safety Executive and intended to protect people working in construction and others who may be affected by their activities. The Regulations require the systematic management of building projects from concept to completion and throughout the life cycle of the building, including the eventual demolition. They also require designers and those who control or carry out construction work to identify hazards associated with their designs or work (including risk from fire) and plan to eliminate, control or reduce the risks. In Northern Ireland, health and safety issues are addressed through a series of Health and Safety Orders which mirror the provisions of the Health and Safety at Work etc Act 1974 and its associated regulations. The standards and requirements are intended to be identical to those in Great Britain. There is a separate agency with its own inspectors which includes specialist fire surveyors.

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8.4.2 Houses in multiple occupation One particular area of concern is with “Houses in Multiple Occupation” (HMOs), which are defined as dwellings where the members of more than two families live together sharing facilities. Sharing facilities generally refers to shared bathrooms, kitchens or living rooms. They cover everything from student flats, to shared flats occupied by professionals, to those which might offer accommodation for recently released prisoners and those needing mental health support. Each jurisdiction has legislation for their registration and requires minimum standards of various items including fire safety. Draft guidance is published, however as the licensing authorities are normally the local councils the actual standards can vary considerably and fire authorities are often given the right of comment on HMO registration applications. 8.4.3 Licensing Under the various Licensing Acts in force in different parts of the United Kingdom the fire authorities can object to the issue of a licence if the means of escape, or other fire precautions, are not satisfactory or there is undue risk of fire in the premises. Licences are normally given by the Licensing Court (Licensing Justices), who must consult the fire authority. The fire authority makes observations and the court makes a ruling which may include requirements to alter the premises. An applicant can normally appeal to the court within a set time if unhappy. The premises covered are those licensed for the sale of alcohol, for gambling (including bingo), and for certain other licensed activities. Some activities are licensed directly by local councils, such as theatres, cinemas, places of public entertainment, under a very similar process. In most cases the relevant guidance is the same as that used generally for existing buildings. 8.4.8 Local legislation As well as the national legislation which has been mentioned, there is also a vast body of local legislation concerned with fire safety. Many local authorities still have powers invested in them in respect of fire safety for different building types. Some local Acts were introduced at the beginning of the last century and many were transferred from the old authorities to their successors when local government re-organisation occurred in 1974 and again in the 1990s. Much has been repealed in the recent Fire Acts for both England and Wales and Scotland, but some still remains to catch the unwary. 8.4.9 Other legislation Fire safety provisions are also attached to a plethora of Acts often related to specific building types or specific activities, including:

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British Standards and International Standards

• • • • • • • • • • •

animal boarding establishments caravan sites children’s homes community care homes educational buildings explosives factories and workplaces firework factories mines and quarries nurseries petroleum installations pipe lines.

8.5 British Standards and International Standards The British Standards Institution 389 Chiswick High Road, London W4 4AL 020 8996 7001 www.bsigroup.co.uk British Standards are published by the British Standards Institution (BSI) and they are prefixed with the letters BS. Where they are accepted as common across Europe the designation becomes BS-EN. International standards are published by the International Organisation for Standardisation and are prefixed by the letters ISO. In every case the most recent amendment must always be the one which is used. The first sub-section covers design guides, which the architect may wish to consider and the set of structural Euro-codes. The second sub-section consists of the test methods which will be referred to in the design guides, but the details of which architects and designers should not need to know in detail. The final sub-section covers standards of peripheral interest. In each case the British Standards are listed first and then the European and, if appropriate, the international ones. 8.5.1 Design guides, fire risk assessment guides and standards BS 7974: 2001 – Application of fire safety engineering principles to the design of buildings – Code of practice This is the principal British Standard on fire safety engineering and is aimed primarily at specialists as it is more advanced and detailed than BS 9999, which is designed for a wider range of buildings and a more general audience. It comprises a Code of Practice and a series of published documents (PDs) on the subsystems, in an attempt to codify the principles of fire engineering design as it applies to buildings. It is widely used by fire engineers and generally respected not only in the UK, but also in other countries. PD 7974-0: 2002 – Guide to design framework and fire safety engineering procedures PD 7974-1: 2003 – Initiation and development of fire within the enclosure of origin (sub-system 1)

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PD 7974-2: 2002 – Spread of smoke and toxic gases within and beyond the enclosure (sub-system 2) PD 7974-3: 2003 – Structural response and fire spread beyond the enclosure of origin (sub-system 3) PD 7974-4: 2003 – Detection of fire and activation of fire protection systems (sub-system 4) PD 7974-5: 2002 – Fire s ervice intervention (sub-system 5) PD 7974-6: 2004 – Human factors: life safety strategies, occupant behaviour and condition (sub-system 6) PD 7974-7: 2003 – Probabilistic risk assessment PD 7974-8: 2012 – Property protection, business and mission continuity and resilience BS 9999: 2008 – Code of practice for fire safety in the design, management and use of buildings This is the principal British Standard on general fire safety design engineering and is aimed primarily at a more general readership than the more advanced and detailed BS 7974, which is primarily for fire safety engineers. It replaced all of the BS 5588 series plus many associated fire safety standards. When it was planned it had been envisaged that this might be given the status of an Approved Document in England and Wales and, has already been mentioned, recognised by Scottish Ministers. The following set of linked European Standards are part of the European structural codes and cover the structural fire design of different building materials across Europe. Each of which has a section on structural fire design. BS EN 1991: Actions on structures BS EN 1992: Design of concrete structures BS EN 1993: Design of steel structures BS EN 1994: Design of composite steel and concrete structures BS EN 1995: Design of timber structures BS EN 1996: Design of masonry structures PAS 79: 2012 – Fire risk assessment – Guidance and a recommended methodology This publicly available specification (PAS) was first prepared in 2005 by CS Todd and Associates Ltd, revised in 2007 and now published under licence from the BSI. It is well respected and offers a logical and structured approach to undertaking fire risk assessments required for most public buildings under United Kingdom law. 8.5.2 Test methods and specifications BS 476: Fire Tests on Building Materials and Structures Part 3: 2004 – External fire exposure roof test This test assesses the ability of a roof structure to resist penetration by fire when the outer surface is exposed to radiation and flame, and the likely extent of surface ignition during penetration. Roof structures are classified according to the actual times recorded, for example a “P60” designation means that the sample

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of roof resisted penetration for at least 60 minutes. Roof classifications are prefixed by a designation showing whether it was tested as a sloping (S) or flat (F) construction. Part 4: 1970 – Non-combustibility test for materials This test assesses whether materials are non-combustible by seeing if samples will give off heat or flame when heated. Part 6: 1989: 2009 – Method of test for fire propagation for products This test assesses the contribution of combustible materials to fire growth when they are subjected to flame and radiant heat. Part 7: 1997 – Method of classification of the surface spread of flame of products This test assesses the spread of flame across flat materials (normally wall or ceiling linings) when they are subjected to flame and radiant heat. Materials are classified as follows: Class

Max flame spread at 1.5 min

10 min

1

165 mm

165 mm

2

215 mm

455 mm

3

265 mm

710 mm

4

900 mm

900 mm

Part 11: 1982 – Method for assessing the heat emission from building products This test is a development of the basic test for non-combustibility in Part 4, and it quantifies the level of heat given off by a material when it is heated. Part 20: 1987 – Method for determination of the fire resistance of elements of construction (general principles) Part 21: 1987 – Method for determination of the fire resistance of loadbearing elements of construction Part 22: 1987 – Method for determination of the fire resistance of non-loadbearing elements of construction Part 23: 1987 – Method for determination of the contribution of components to the fire resistance of a structure These tests assess the fire resistance of different elements of construction and they replace Part 8 (1972 – Test methods and criteria for the fire resistance of elements of building construction). The length of time for which the building elements can satisfy the following criteria, under test conditions, is recorded:

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• • •

loadbearing capacity (supporting the test load without excessive deflection) integrity (resisting collapse, the formation of holes, and the development of flaming on the unexposed face) insulation (resisting an excessive rise in temperature on the unexposed face).

Test results are normally expressed for each of the criteria in minutes. Columns and beams only have to satisfy the loadbearing criteria, glazed elements normally only have to satisfy the integrity criteria, while floors and walls have to satisfy all three criteria. Part 24: 1987 – Method for determination of the fire resistance of ventilation ducts This test assesses the ability of ductwork to resist the spread of fire from one compartment to another without the assistance of dampers. Results are given in minutes for each of the criteria of stability, integrity and insulation. It is identical to ISO 6944: 1985 – Fire resistance tests. Ventilation ducts. Section 31.1: 1983 – Methods for measuring smoke penetration through doorsets and shutter assemblies. Method of measurement under ambient conditions Based on Part 1 (1981), the ambient temperature test, of ISO 5925: Fire tests. Evaluation of performance of smoke control door assemblies. This test assesses the likely amount of smoke penetration through shut doorsets and shutter assemblies. Results are given in air leakage in cubic metres per hour. BS 4790: 1987 – Method of determination of the effects of a small ignition source on textile floor coverings (hot metal nut method) BS 5438 1989 (1995) – Methods of test for flammability of fabrics when subjected to a small igniting flame applied to the bottom edge of vertically orientated specimens BS 5852: 2006 – Methods of test for assessment of the ignitability of upholstered seating by smouldering and flaming ignition BS 7177: 2008 +A1 2011 – Specification for resistance to ignition of mattresses, mattress pads, divans and bed bases BS 8414: Fire performance of external cladding systems Part 1: 2002 – Test method for non-loadbearing external cladding systems fixed to the face of the building Part 2: 2005 – Test method for non-loadbearing external cladding systems fixed to and supported by a structural steel frame

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BS EN ISO 1182: 2010 Reaction to fire tests for building products – Noncombustibility test The following set of linked European Standards (1363–1366) are now the basis of fire resistance test specification for buildings across Europe. BS EN 1363: Fire resistance tests 1: 2012 – General requirements 2: 1999 – Alternative and additional procedures BS EN 1364 : Fire resistance tests for non-loadbearing elements 1: 1999 – Walls 2: 1999 – Ceilings BS EN 1365: Fire resisting tests for loadbearing elements 1: 2012 – Walls 2: 2000 – Floors and roofs 3: 2000 – Beams 4: 1999 – Columns BS EN 1366: Fire resistance tests for service installations 1: 1999 – Ducts 2: 1999 – Fire dampers BS EN 1634: Fire resistance and smoke control tests for door and shutter assemblies – openable windows and elements of building hardware 1: 2008 – Fire resistance tests for doors, shutters and openable windows 2: 2008 – Fire resistance characterisation test for elements of building hardware 3: 2004 – Smoke control test for door and shutter assemblies BS EN ISO 1716: 2010 – Reaction to fire tests for building products – Determination of the gross (calorific value) BS EN ISO 11925: Reaction to fire tests 2: 2010 – Ignitability of products when subjected to direct impingement of a flame. Single flame source test BS EN 13501 : Fire classification of construction products and building elements 1 : 2007 + A1: 2009 – Classification using test data from reaction to fire tests 2 : 2007 + A1: 2009 – Classification from data from fire resistance tests, excluding ventilation services 3 : 2005 + A1: 2009 – Classification using data from fire resistance tests on products and elements used in building service installations: fire resisting ducts and dampers 4 : 2007 + A1: 2009 – Classification using data from fire resistance tests on components of smoke control systems 5 : 2005 + A1: 2009 – Classification from data using external exposure roof tests

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Information

BS EN 13823 : 2010 Reaction to fire tests for building products. Building products excluding flooring exposed to the thermal attack by a single burning item 8.5.3 Other standards of peripheral interest BS 3251: 1976 Indicator plates for hydrants and emergency water supplies BS 4422: 2005 Fire – Vocabulary BS 5041: Fire Hydrant Systems Equipment Part 4: 1975 (1987) – Specification for boxes for landing valves for dry risers BS 5266: Emergency Lighting Part 1: 2011 – Code of practice for the emergency escape lighting of premises BS 5268: Code of Practice for the Structural Use of Timber Section 4.2: 1990 – Recommendations for calculating fire resistance of timber stud walls and joisted floor constructions BS 5306: Code of practice for fire extinguishing installations and equipment on premises Part 0: 2011 – Guide for the selection of installed systems and other fire equipment Part 1: 2006 – Hose reels and foam inlets Part 4: 2001 +A1 2012 – Specification for carbon dioxide systems BS 5395: Stairs, lobbies and walkways Part 2: 1984 – Code of practice for design of helical and spiral stairs Part 3: 1985 – Code of practice for the design of industrial type stairs, permanent ladders and walkways BS 5446: Specification for components of automatic fire alarm systems for residential premises Part 2: 2003 – Fire detection and alarm devices for dwellings. Specification for heat alarms Part 3: 2005 – Fire detection and alarm devices for dwellings. Specification for smoke alarm kits for deaf and hard of hearing people BS 5499 : Graphical symbols and signs. Safety signs, including fire safety signs Part 4: 2000 – Code of practice for escape route signing BS 5839: Fire detection and alarm systems for buildings Part 1: 2002 – Code of practice for system design, installation and servicing Part 3: 1988 – Specification for automatic release mechanisms for certain fire protection equipment Part 6: 2004 – Code of practice for the design and installation of fire detection and alarm systems in dwellings 126

British Standards and International Standards

Part 9: 2011 – Code of practice for the design, installation, commissioning and maintenance of emergency voice alarm systems BS 5979: 2000 Code of practice for remote centres for alarm systems BS 6266: 2011 Fire protection for electronic equipment installations. Code of practice BS 6336: 1982 Guide to development and presentation of fire tests and their use in hazard assessment BS 6440: 2011 Powered lifting platforms having non-enclosed or partially enclosed liftways intended for use by persons with impaired mobility. Specification BS 7273: Code of practice for the operation of fire protection measures Part 4: 2007 – Actuation of release mechanisms for doors BS 8202: Coatings for fire protection of building elements Part 1: 1995 – Code of practice for the selection and installation of sprayed mineral coatings Part 2: 1992 – Code of practice for the use of intumescent coating systems BS 8214: 2008 Code of practice for fire door assemblies BS 8313: 1997 Code of practice for accommodation of building services in ducts BS 9251: 2005 Sprinkler systems for residential and domestic occupancies. Code of practice BS 9990: 2006 Code of practice for non-automatic fire-fighting systems in buildings BS EN 54-11: 2001 Fire detection and alarm systems – manual call points BS EN 81: Safety rules for the construction and installation of lifts 1: 1998 – Electric lifts 2: 1998 – Hydraulic lifts 58: 2003 – Examination and tests. Landing doors fire resistance BS EN 179: 2008 Building hardware – emergency exit devices operated by a lever handle or push pad for use on escape routes – requirements and test methods

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Information

BS EN 1125: 2008 Building hardware – panic exit devices operated by a horizontal bar, for use on escape routes – requirements and test methods BS EN 1155: 1997 Building hardware – electrically powered hold open devices for swing doors – requirements and test methods BS EN 1838 1999 (BS 5266-7: 1999): Lighting applications – emergency lighting BS EN 12101: Smoke and heat control systems 3: 2002 – Specification for powered smoke and heat exhaust ventilators 6: 2005 – Specification for pressure differential systems. Kits BS EN 12416: Automatic fire suppression 2: 2001 – Powder systems. Design, construction and maintenance BS EN 12845: 2004 +A2 2009 Fixed fire-fighting systems. Design, installation and maintenance 8.6 Guidance The amount of guidance available to the design team is deceptively extensive. There are a large number of government organisations, trade associations and private companies offering information, guidance and advice on fire safety; however, this information is of variable quality and extremely patchy in its coverage. Some areas are very well covered (e.g. auto-suppression systems), while in other fields (e.g. smoke control) there is only a scattering of experts and information useable by the design team. One of the problems facing the architect is establishing what information is reliable and trustworthy, and where there is a need to take further more specialist advice. This section cannot hope to cover all the guidance which is available, but it does seek to consider the main sources of information and to identify the most recent and useful publications from these different sources. Where the title of documents is not completely self-explanatory an additional note has been added to guide designers as to the relevance and application of the materials. The guidance has been listed under the organisation producing it as this is the most likely way that designers will be able to trace what they need. It would have been possible to organise materials by reference to the fire safety tactic to which they relate, but this would have resulted in considerable duplication. The useful life of a code or guide is only about ten years and therefore there is a continually shifting body of information. However, as specific documents go out of date they are likely to be replaced by the organisation concerned, another reason for structuring this section by organisation. Addresses and contact details are also included wherever possible to enable practices to obtain their own copies of key documents.

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Guidance

8.6.1 BRE BRE, Bucknalls Lane, Watford WD25 9XX 01923 664100 [email protected] The BRE Group is now an independent research and testing organisation for building science. It has brought together a number of building research and related organisations and now operates in the public interest as a group of companies with the profits ploughed back into research and education in the field of the built environment. The Fire Research Station became a part of the then Building Research Establishment in 1972 and later moved to share the same site. BRE has a large staff, many of whom work in the field of fire safety. It has the largest fire testing Burn Hall in Europe and in the past has used even larger spaces for full-scale reconstructions and test burns. For a time it was able to use the old airship hanger at Cardington which is capable of taking reconstructions of complete buildings. After the Rosepark care home fire a full-scale reconstruction of the affected floor was built in a large space normally used for ship and oil rig construction and three tests were carried out to understand better what had happened and whether the presence of sprinklers or the closing of the bedroom doors would have significantly changed the course of the fire and the level of fatalities (see section 4.1.1). The Loss Prevention Council (which had developed from the Fire Officers’ Committee) was an authoritative organisation producing rules and standards for fire fighting products. Its certification arm (the Loss Prevention Council Certification Board), became part of BRE Certification in 2000 and is now based on the same site. BRE is of value to architects both through its library and consultancy services, and because of its numerous publications. Many of these publications are research reports of limited value to architects in practice, but certain of their publications are useful reference documents and the designer may well find them being referred to by the statutory authorities when assessing designs. Some are fullscale books or reports, and others shorter works (digests) or single sheet information papers. The following list is far from comprehensive, but does identify the ones liable to be of some use in the design process. Key publications for the design team are as follows: Multi-storey timber frame buildings: a design guide (BR 454), R Grantham et al, published jointly with TRADA, 2003 Structural fire engineering design: introduction, T Lennon 2003

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Information

Structural fire engineering design: materials behaviour – concrete, T Lennon, 2004 Structural fire engineering design: materials behaviour – timber,J Bregulia et al, 2004 Structural fire engineering design: materials behaviour – steel, C Bailey, 2004 Structural fire engineering design: materials behaviour – masonry, R de Vekey, 2004 Structural fire engineering design: aspects of life safety, D Purser, 2004 Structural fire engineering design: fire and thermal response, S Welch, 2004 Structural fire engineering design: fire development, T Lennon, 2004 Fire modelling, G Cox, 2004 Concrete structures in fire: performance, design and analysis, T Lennon et al, 2007 Fire safety and security in places of worship, 2009 Automatic fire sprinkler systems: a good practice guide, C Williams, 2009 Fixed gas extinguishing systems for fire protection, L Jackman, 2009 Sprinkler systems explained: a guide to sprinkler installation standards and rules, 2009 Lessons learned from real fires, M Shipp, 2010 Sprinkler systems for the fire protection of commercial and industrial buildings, L Jackman, 2010 Evacuation modelling and human behaviour in fire, J Fraser-Mitchell and D Charters, 2010 Fire performance of insulated structural panel systems, T Lennon and D Hopkin, 2010 An introduction to the use of fire modelling, R Chitty, 2010 Design fires for use in fire safety engineering, C Mayfield and D Hopkin, 2010 Structural fire engineering, T Lennon, 2011 Residential sprinklers for fire protection, C Williams, (revised) 2012 Fire performance of light steel framed structures, T Lennon and D Hopkin, 2012

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Passive and reactive fire protection to structural steel, T Lennon and D Hopkin, 2012 Domestic smoke alarms, E Warren, 2012 Fire doors, N Macdonald and A Russell, 2012 Fire performance of external thermal insulation for walls of multi-storey buildings, S Colwell and T Baker, (Third edition) 2013 External fire performance of roofs: a guide to test methods and classifications, S Colwell and T Baker, 2013 Evacuating vulnerable and dependant people from buildings in an emergency, D Crowder and D Charters, 2013 8.6.2 Fire Protection Association FPA, London Road, Moreton in Marsh, Gloucestershire GL56 0RH 01608 812 500 [email protected] The Fire Protection Association (FPA) has a long history of working for building fire safety and is closely connected with the insurance industry. It was a part of the Loss Prevention Council until 2000, when the certification part of that was sold to BRE. The FPA now concentrates on ensuring a convergence of government fire safety objectives (life safety) with those of insurance and business (life safety and business and property protection). The FPA develops and maintains a number of key insurer standards for the implementation of active and passive fire protection requirements. It also offers education and training and has an extensive library. Key publications for the design team: Guide to fire safety signs (FSB 36), 2007 LPC Rules for Sprinkler Installations, 2009 The prevention and control of arson (FSB 40), (Third edition) Passive fire protection handbook (FSB 61), 2011 Emergency lighting handbook (FSB 63), 2012 Approved Document B: Fire safety (Volume 2) – Buildings other than dwellinghouses (ADBFIRESAFETY) This is an enhanced version of the Approved Document which includes extra insurance orientated technical guidance.

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8.6.3 Department of Health “Firecode – Fire safety in the NHS” consists of a number of Health Technical Memoranda (HTM) produced by the Department of Health which, in the 05 series, provide technical guidance on the specialist aspects of fire safety for NHS healthcare premises. They apply in England and Wales and there are variants of some of them in use in other parts of the United Kingdom. Key publications for the design team: HTM 05-01 Managing healthcare fire safety, 2006 HTM 05-02 Guidance to support functional provisions in healthcare premises, 2007 This is the most important as, at publication, it had the same status as Approved Document B thereby offering the designer the certainty of complying with the Building Regulations. HTM 05-03 Operational provisions – Part B Fire detection and alarm systems, 2007 HTM 05-03 Operational provisions – Part D Commercial enterprises on healthcare premises, 2007 HTM 05-03 Operational provisions – Part E Escape lifts on healthcare premises, 2006 HTM 05-03 Operational provisions – Part G Laboratories on healthcare premises, 2007 8.6.4 Department of Education Building work at all state schools in England must comply, not only with the Building Regulations, but also follow “Building Bulletin 100: Design for fire safety in schools” (RIBA Enterprises, 2007), which provides the normal method of compliance and sets out the Department of Education’s policy on sprinklers in schools. The previous guidance (Fire and the Design of Educational Buildings, Building Bulletin 7, HMSO, 1988) is still relevant as it applied to many of schools when they were being built. Building Bulletin 7 was first published in 1952 and was regularly updated. It was primarily aimed at new design work, but could also be appropriate in the context of alterations to existing buildings. Fortunately it had an excellent “first principles” approach and is clearly illustrated and explained. It covered: • • • • •

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means of escape; precautions against fire; structural fire precautions; fire warning systems and fire fighting; and fire safety management issues within the buildings.

Guidance

It is worth noting that there are specific legislative requirements within Regulation 17 of the School Premises Regulations, 1999. 8.6.5 Timber Research and Development Association Timber Research and Development Association Stocking Lane, Hughenden Valley, High Wycombe, Buckinghamshire HP14 4ND 01494 569600 [email protected] The Timber Research and Development Association (TRADA) is a research and testing organisation for the timber industry. It produces a series of valuable publications for architects, especially the Wood Information Sheets (WIS). Its fire testing division now operates as Chiltern International Fire which undertakes commercial and bespoke testing. TRADA also has a commercial consultancy and research company, TRADA Technology. All these organisations are based on the same site. Key publications for the design team are as follows: Fire resisting door sets by upgrading (WIS 1-32), TRADA, 2005 Performance of fire resisting doorsets (WIS 1-13), TRADA, 2005 Wood based panel products and timber in fire (WIS 4-11), TRADA 2008 Timber frame walls and floors: fire resistance of service penetrations (RR 1/2001), TRADA, 2001 Reinstatement of timber frame buildings after fire (RIS 1/2002), TRADA, 2002 Timber fire resisting doorsets (Report 1/2002), TRADA, 2002 Multi-storey timber frame buildings (BR 454) TRADA published jointly with BRE, 2003 Fire performance of timber frame dwellings (WIS 4-30), TRADA, 2012 Reaction to fire: testing and classification (TI-0803), Chiltern International Fire, 2008 Historic buildings and fire safety (TI-0810), Chiltern International Fire Fire resistance: testing, assessment and certification (TI-080), Chiltern International Fire, 2009 Fire resistance : service penetration seals testing (TI-1004), Chiltern International Fire, 2010

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Fire resistance: design considerations (TI-1002), Chiltern International Fire, 2010 Fire doors: for the health sector (TI 1014), Chiltern International Fire, 2010 8.6.6 Steel Construction Institute Steel Construction Institute Silwood Park, Ascot, Berkshire, SL5 7QN. 01344 636525 [email protected] The Steel Construction Institute (SCI) is a research and development organisation for the steel construction industry. It has produced a number of useful detailed documents on the fire protection of steelwork, as well as a number of Technical Reports giving test data and excellent fire reports. Key publications for the design team are as follows: Designing for structural fire safety. A handbook for architects and engineers (P1970), 1999 Basic information for architects and engineers to help them understand the principles behind the fire safety design of structures. Fire resistant design of steel framed structures (P375), 2012 General overview of structural fire safety in accordance with the Eurocodes. Design of steel framed buildings without applied fire protection (P186), 1999 As the title says, a guide as to how far it is possible to design structural frames without needing to apply additional fire protection. 8.6.7 Textbooks There are surprisingly few textbooks on the fire safety of buildings and anything published more than ten years ago, although fine for basic information, cannot be relied upon for the legislative position. Key publications for the design team, though in most cases only parts will be relevant, are as follows: Structural Design for Fire Safety, A Buchanan, Wiley, 2001. A general textbook on the principles of structural fire safety which is not country specific and covers the main structural materials. Fire Safety Engineering (CIBSE Guide E), Chartered Institute of Building Services Engineers, Third edition 2010. Useful practical advice on fire engineering intended for the engineer. An Introduction to Fire Dynamics, D Drysdale, Wiley, Third edition 2011. For 25 years this has been the acknowledged authoritative textbook on fire

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science. However, this is probably a book for the fire scientist and fire engineer rather than the designer. Fire Safety Engineering. Design of Structures, JA Purkiss, Routeledge, 2006 A textbook focusing on the fire section of the Structural Eurocodes, this could be useful for fire engineers or structural engineers. Quantitative Risk Assessment in Fire Safety, G Ramachandran and D Charters, Routledge, 2011 This book is intended to be an expanded version of Part 7: Probabilistic risk assessment, a Published Document to BS 7974, with which the authors were very closely involved. Evaluation of Fire Safety, D Rasbash et al, Wiley, 2004 A book by many of the authoritative figures who developed the discipline of fire safety engineering. This is for fire safety engineers rather than the design team. Design Against Fire, P Stollard and L Johnston (eds), E & FN Spons, 1993 Although now a little dated this book is unique in being based on the keynote papers in an innovative postgraduate fire engineering course held at Queen’s University, Belfast. It presents the collected views of the leading experts in fire safety engineering including: J Abrahams, J Anderson, D Drysdale, L Johnston, W Malhotra, H Morgan, J Northey, J Sime and P Stollard. Comprehensive Guide to Fire Safety, C Todd, BSI, Second edition 2000. Intended as a basic guide for the non-specialist, it is by one of the leading fire safety engineers working in the United Kingdom who has been at the forefront of work on standards and codes of practice for many years. There are also a number of excellent books and codes in the United States which might be of interest to fire safety engineers. The National Fire Protection Association of America (NFPA) publications are an extremely useful source of information, in particular:

• • •

Fire Code, 2012, National Fire Protection Association, Quincy, MA. Life Safety Code, 2012, National Fire Protection Association, Quincy, MA. Building Construction and Safety Code, 2012, National Fire Protection Association, Quincy, MA.

The International Code Council’s (ICC) publications are also extremely useful, in particular: •

International Building Code, 2012, International Code Council, Washington, DC.

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Information

• •

International Building Code, International Code Council, Washington, DC. ICC Performance Code for Buildings and Facilities, 2012, International Code Council, Washington, DC.

The background, contents and role of these American documents is discussed in detail in Chapter 9. 8.7 Consultancy and advisory services The previous sections have all dealt with written guidance materials, but it may be necessary for the design team to seek direct help from a fire safety consultancy. In this case there are a number of options for the design team to consider. Both the BRE and FPA offer providing advisory services on a consultancy basis. This can be on a number of levels. At its simplest their respective library services will assist architects and designers to find the correct documents and guidance from among both their own and any other publications. They also offer a technical consultancy which will advise directly on the fire engineering of a particular design. This might range from the complete integrated smoke control system, to the likely performance of a single component or assembly. They both have expert staff and extremely good test facilities for experimental work. Most architects who seek fire safety advice will approach one of the independent fire safety consultancies now working in this field. As with all consultants, some are excellent and some are little more than charlatans. It is essential for the architect to decide what service they need and therefore the right consultancy to provide such services; it may be that the architects are only seeking someone to check their own designs for legislative compliance, or they may need to use chartered fire engineers who would be capable of the much more demanding task of preparing a full fire engineering solution to an unusual design problem. The principal organisations representing fire safety consultants have merged over the last few years and this has enabled them to gain recognition from the Engineering Council. Therefore designers wishing to appoint a chartered fire engineer should approach the Engineering Council Division of the Institution of Fire Engineers (IFE). However, it is important to note that not all members are Chartered Engineers and both their Consultants directory and register of Fire Risk Assessors is wider than just chartered fire engineers. The IFE offices are at: IFE House, 64–66 Cygnet Court, Timothy’s Bridge Road, Stratford-upon-Avon, CV37 9NW 01789 261 463 [email protected] Although trade associations are established to serve the interests of their members and therefore may not always offer completely independent

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Consultancy and advisory services

advice, they can provide a useful source of information to designers. This is particularly true when it comes to the selection of materials or components to meet an already determined specification. Trade associations in the field of fire safety which architects might wish to consult are as follows: Association for Specialist Fire Protection Kingsley House, Ganders Business Park, Kingsley, Bordon, Hampshire GU 9LU 01420 471 612 [email protected] Fire Industry Association Tudor House, Kingsway Business Park, Oldfield Road, Hampton, Middlesex TW12 2HD 020 3166 5002 [email protected] European Federation of Fire Separating Element Producers 20 Park Street, Princes Risborough, Buckinghamshire HP27 9AH 01844 275500 Glass and Glazing Federation 54 Ayres Street, London SE1 1EU 0207 939 9101 [email protected] Intumescent Fire Seals Association 20 Park Street, Princes Risborough, Buckinghamshire HP27 9AH 01844 274002 [email protected] It is also important to include CERTIFIRE, this is an independent certification scheme run by Warrington certification (01925 646 669) certifire@ warringtonfire.net. Finally there is FireNet ([email protected]) a useful source of information contacts, news and listing of advice sources.

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Chapter 9

A brief overview of the building regulatory system in the United States Brian J. Meacham

In this chapter the building regulatory system in the United States will be considered. It is prescriptive, complex and unlike the systems in most other countries, even though countries with federal-type systems (including Australia, Austria and Canada) have similar challenges in terms of regulatory development, adoption, implementation and enforcement. There is no federal requirement for building regulation. There is no federal agency responsible for building regulation. There is no national building code. Therefore there can be significant variation in building code requirements, application and enforcement from one part of the country to another. There is no federal system because states have the constitutional right to regulate for the health, safety and welfare of their citizens, which includes building and fire regulation and enforcement. There can be wide variation between states due to climatic conditions, the history of building code development and implementation across the United States, and that fact that most state and local building codes are based on “model” building codes and “consensus” standards, which are developed by the private sector and adopted into law at a state and local level, with or without modification. This decentralization of regulatory power, coupled with private sector development of model codes and standards, results in a number of difficult issues, including: a complex interaction of state and local laws and ordinances; separate building and fire codes; numerous reference standards and non-regulatory design guidelines; requirements for registration and licensing of professionals; and government enforcement. The complexity in the building regulatory system, along with the litigious nature of the construction sector, has also meant that adoption of a completely 138

Legal basis, roles, responsibilities and structure of building regs

performance-based building regulatory system has not yet occurred, and is not likely to occur in the near future. 9.1 Legal basis, roles, responsibilities and the structure of building regulations One of the fundamental principles of the Constitution of the United States is that only a specific set of powers is delegated to federal government, and the balance of power is reserved for the people, who, within their states, may delegate any authority they wish to state government through the state legislature (1). This was made clear by the Tenth Amendment to the Constitution, which stipulates “the powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people” (2). An important power that the people have delegated to their respective states, through state constitutions, is police power: the authority for states to regulate for the health, safety and general welfare of its citizens (3),(4). Many of the laws enacted by states in the 1800s and early 1900s, such as public health and quarantine laws, general penal laws, and public works laws are of this type (1). As building codes are concerned with the health, safety and general welfare of the public, the police power is the source of all authority to enact building and fire codes. A state, or more accurately the people within a state, further have the right to delegate certain powers to local or regional governments (e.g. municipalities or counties) under what is known variously as the Ultra Vires Rule, Dillon’s Rule or Home Rule (6),(2),(4). The Ultra Vires Rule, based on the Tenth Amendment to the Constitution, holds that political subdivisions possess only the powers expressly conferred by charter or law and no other powers (2). This means that local governments may only exercise those powers specifically granted to them by state constitutions. The extent to which local jurisdictions have been granted home rule, or the power to exercise local control, varies by state, with Texas giving cities the most freedom and Vermont constitutionally reserving all governmental control (2). Building and fire codes become legally enforceable when incorporated into state or local laws or ordinances. While this is a legislative activity, most building and fire codes are initially developed by local or state “commissions” or “boards” established specifically for code development purposes (e.g. a building code commission, a fire code commission, etc). These commissions typically include representatives of the affected industry (e.g. building and fire safety) and of the public, and have the responsibility for assessing local needs, reviewing code options, and recommending codes to the state legislature or local government for adoption into law (Figure 9.1). The degree to which a distinction is made between building and fire code applicability and enforcement is based on several factors, including what model codes are adopted (if any), the type and extent of local revisions, and who has enforcement responsibilities. (Model codes and their adoption is discussed

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A brief overview of the building regulatory system in the USA

US Constitution

Legislation (Laws)

State Constitution

Code Commission

Legislation (Ordinances)

Local Jurisdiction

Code Commission

Implementation, plan review, enforcement...

Building Department

below). At the state and/or local level, there are often at least two departments with regulatory authority with respect to building construction and fire safety: the Building Department (or similar government entity, such as Development Services, Building Control, etc) and the Fire Department (or similar government entity (e.g. Department of Public Safety, Department of Fire Services, etc). The Building Department typically has the power to issue building permits, accept designs, and approve construction documents (7). Through the course of construction, the Building Department is typically responsible to ensure the building design meets the applicable codes, and that the actual constructed building meets the design documentation. Once the final building has been inspected and approved, a Certificate of Occupancy is issued, allowing the building to be occupied and used. Larger building departments typically have staff with expertise on all facets of building construction, including architecture, engineering and associated trades (e.g. plumbing, mechanical and electrical), and review, inspection and approval responsibilities are delegated accordingly. In smaller departments a single person may hold all of these responsibilities. Once the building becomes occupied, the Fire Department typically has the power to ensure that there are no undue fire and explosion hazards, and that the building continues to be safe for human occupancy. Where significant fire

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9.1 Building regulatory structure

Legal basis, roles, responsibilities and structure of building regs

hazards or risks can be expected in the building, based on its intended use (e.g. storage of flammable or explosive materials, use of hazardous processes), certain fire code provisions may be applied to the design and construction of the building. In other cases, the fire code is applied primarily after the building is occupied to ensure safety, for example, to determine that exits remain unlocked, combustible material is not stored in egress paths, and so forth. In larger fire departments, there is typically one or more fire protection engineers involved in review and inspection activities. In smaller departments, this responsibility is carried out by firefighters, who may not have any formal education in hazard or risk assessment. In some jurisdictions, responsibility for building code and fire code development, promulgation and enforcement is under a single entity (e.g. a Department of Public Safety) while in other jurisdictions the responsibilities are completely separated (e.g. a “Building Code Commission” or equivalent, which may be under an “Office of Economic Development” or similar entity, may develop, promulgate and enforce the building code, and a “Fire Code Commission” or equivalent, which may be under the “State Fire Marshal’s Office” or other entity, may develop, promulgate and enforce the fire code). The basis for the operational structure in a state or local jurisdiction is generally rooted in constitutional language. To ease the burden of building and fire code development by state and local officials, “model” codes are widely used. In general, a model code is a set of suggested rules developed by a committee of individuals who have specific expertise in the regulated area, which serves as the basis or model for an enforceable regulation. The primary model building code in the United States is the International Building Code, developed by the International Code Council (Washington, DC) and published in 2012. The International Code Council is a member-focused association dedicated to helping the building safety community and construction industry provide safe, sustainable and affordable construction through the development of codes and standards used in the design, build and compliance process. Fifty states and the District of Columbia have adopted these codes at the state or jurisdictional level. Federal agencies including the Architect of the Capitol, General Services Administration, National Park Service, Department of State, US Forest Service and the Veterans Administration also enforce these codes. The Department of Defense references the International Building Code for constructing military facilities, including those that house US troops, domestically and abroad. Puerto Rico and the US Virgin Islands enforce one or more of the I-Codes. The International Building Code is a prescriptive document with over 600 pages of information presented in 35 chapters plus appendices. (The structure of the International Building Code and the detail of the code is discussed later in this chapter.) The International Code Council separately publishes the ICC Performance Code for Buildings and Facilities, which is not yet adopted and enforced, but is used administratively in several jurisdictions to help guide alternative (performancebased) designs. Although the International Building Code is the primary model building code, there is also NFPA 5000, Building Construction and Safety Code (2012), a model

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A brief overview of the building regulatory system in the USA

building code developed by the National Fire Protection Association (NFPA) and published in Quincy, MA. The mission of the international non-profit NFPA, established in 1896, is to reduce the worldwide burden of fire and other hazards on the quality of life by providing and advocating consensus codes and standard, research, training and education. A leading advocate of fire prevention and an authoritative source on public safety, NFPA develops, publishes, and disseminates more than 300 consensus codes and standards intended to minimize the possibility and effects of fire and other risks. NFPA membership totals more than 70,000 individuals around the world. NFPA 5000contains both prescriptive provisions and a performance-based option. There are also two model fire codes in the United States: the International Fire Code, developed by International Code Council, and NFPA 1, Fire Code developed by the NFPA in 2012. Model building codes are developed by committees composed primarily of building code officials and model fire codes are developed by committees primarily composed of fire officials (as explored in more detail later in this chapter). Planning and zoning codes also exist, but these are typically developed and enforced at the local level without using model codes. Model codes are generally adopted by reference into legislation (law, ordinance), and adoption can be with or without modification. When used as the basis for local or state developed legislation, modifications to suit local requirements or desires are generally made by the building or fire code commission or board, as appropriate. Model building and fire codes (as well as the other model codes) reference a wide range of standards. These standards generally fall into one of the following categories (17),(18),(19): •

•

• •

Test or measurement standards that provide information on the acceptability (pass/fail), performance category, usually under some standard condition (e.g. Class A, 1-hour), or to provide data that can be used to determine acceptability or performance. Procedural standards that detail how products or systems are to be installed, used, maintained, tested, or operated to be safe, reliable fit or for the intended use. Interoperability standards that set out a procedure or arrangement that allows products to fit or work together. Standards of professional practice, generally accepted methods of analysis or design, qualifications, processes and documentation thereof.

Unlike most other state and federal regulations in the United States, model building and fire codes, along with the standards referenced by the model codes, are not developed by government agencies, but are developed by private sector codes- and standards-making organizations. This private sector development of regulations, which ultimately have the force of law, is the source of academic, professional and economic concern and confusion. For example, there is some concern that industry drives “voluntary” codes and standards development,

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thus industry concerns take precedent over public concerns (18),(19). On the other hand, there are concerns that codes and standards developed and approved by single groups (e.g. code officials only) do not adequately address industry concerns. While nearly all of these reference standards are developed in the private sector, they can play different roles, and it is not unusual for one standard to reference another. For example, ASTM International, formerly known as the American Society for Testing and Materials (ASTM), develops a wide range of standards regarding how materials are to be tested. These in turn may be used by a testing and approvals laboratory, such as Underwriters Laboratories Inc (UL) or FMGlobal, as the basis for a product listing of performance in accordance with test parameters. Both ASTM and UL standards in turn are often referenced in system-level standards (such as those from NFPA) and the International Building Code, which may require that materials be “tested in accordance” with ASTM standards and “listed for the purpose” by UL or other approved entity. In order to be principally involved in the design of a building, most states require that the architects and engineers be registered or licensed by the state. The process of registration typically requires completion of a course of study in a duly accredited architecture or engineering program, successful completion of one or more examinations (e.g. engineering exams, by discipline, are offered by the National Council of Examiners for Engineering and Surveying), and payment of dues to the state. In most cases, the practice of architecture and engineering is regulated by a set of professional ethics, which require the architect or engineer to limit their work to their area of expertise and competence. In some cases, architects and engineers are given the burden of meeting the intent of building and fire codes by the force of their registrations (i.e. there is no review or approval by the building or fire department). There are also numerous other players in the construction sector which play a role in building design, construction and operation, including professional societies, such as the American Society of Civil Engineers and the American Society of Mechanical Engineers (ASME), which develop design standards and help set competency standards for exams given by the National Council of Examiners for Engineering and Surveying, industry groups, such as the National Electrical Manufacturers Association and the American Gas Association, which represent manufacturing interests, research, academia and the insurance industry. This complex arrangement is illustrated in Figure 9.2. In summary, states have the authority to regulate buildings through the police power granted to them by the US Constitution and its Tenth Amendment. The specific powers for regulation of buildings, within a state, are defined in the State Constitution. A state may, if it chooses, delegate power for regulation of buildings to local jurisdictions through Home Rule ( Ultra Vires Rule, Dillon’s Rule) provisions. Regulation of buildings is typically two-pronged: the building code addresses design and construction (pre-occupancy) and the fire code addresses safety in use. The building and fire codes are generally based on “model” codes, which are developed in the private sector. Code commissions

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9.2 Relationship between Model Codes, Reference Standards and other entities

ICC

IBC

IMC

IPC

IRC

Fire

Structure

Mech.

Plumbing

FM

Codes

Standards NEMA

UL

Engineers

ASTM

NFPA

ASCE

Research

Insurance

Academia

ASME

AGA

Code Officials

Key: FM – FMGlobal; UL – Underwriters Laboratories; ASTM – American Society for Testing Materials; NFPA – National Fire Protection Association; ASCE – American Society of Civil Engineers; ASME – American Society of Mechanical Engineers; NEMA – National Electrical Manufacturers Association; AGA – American Gas Association

or boards will typically be appointed to develop and/or recommend adopting building and fire codes. Building and fire codes reference a wide range of materials, test, procedural, and interoperability standards and standards of professional practice. At the state and/or local level, certain powers for enforcing building and fire regulation will be granted to building and fire departments respectively, including facilitating safety to life, property and community welfare through proper building design, construction, operation and maintenance. By registration, licensing and ethics, architects and engineers have responsibilities for certain building and fire safety decisions. A wide range of professional and industry organizations, as well as insurers, researchers and academics, participate in the codes and standards development process. 9.2 Standards, product certification and evaluation As noted above, in addition to the building code, the building regulatory system in the United States relies on a large number of standards, guides, guidelines and codes of practice to facilitate appropriate design, construction and performance of buildings and building systems. There are several hundred standards referenced by the International Building Code alone. In many cases, the standards referenced in the International Building Code in turn make reference to other standards. While it is difficult to generalize the system (there are always cases that do not fit precisely), one can get a sense of the role of standards, as well as product certification and evaluation, using the taxonomy for types of standards outlined earlier: test or measurement standards, procedural standards, interoperability standards, and standards of professional practice (17). 144

Standards, product certification and evaluation

Taking them in reverse order, standards of professional practice are generally developed within the realm of professional membership organizations – either for specific disciplines or industries – such as the American Society of Civil Engineers, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, the ASME, the American Concrete Institute, the American Institute of Steel Construction and so forth. These types of standards generally outline (or define) the process for design, and may identify design criteria (performance criteria), but generally do not specify in detail how to test, assess or assure performance of products: this is addressed within the realms of procedural standards, test or measurement standards and product certification. Procedural standards are generally developed within industry-based organizations or membership organizations whose members are focused within a particular industry, and are generally product, system or assembly oriented. An example of this would be NFPA 13, Standard for the Installation of Sprinkler Systems (2010). This standard specifies procedures for installation, test and maintenance of sprinkler systems aimed at achieving desired performance. This standard also addresses aspects of sprinkler design, particularly with respect to identifying water flows, pressures, design density and so forth given different building or space hazard classifications, and so is a “cross-over” standard in that regard. This standard does not, however, specify how the individual components in a sprinkler system are to be tested for performance; rather, it states that equipment used must be “listed” for the purpose, where listed is defined as: Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or service meets appropriate designated standards or has been tested and found suitable for a specified purpose. In addition to requirements for being listed, which will be discussed below, there are also requirements for interoperability which are referenced as well. An example is piping materials and fittings. To assure products are compatible, reference is made to specific material standards which define key factors such as materials and dimensions. For example, NFPA 13, paragraph 6.4.1, states that “fittings used in sprinkler systems shall meet or exceed the standards in Table 6.4.1 or be in accordance with 6.4.2 or 6.4.3”. Table 6.4.1 in turn references ASME standards (e.g. ASME B16.3, Malleable Iron Threaded Fittings, Class 150 and 300 Steel) and ASTM standards (e.g. ASTM A 234, Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service). These exemplar ASME and ASTM standards illustrate how interoperability standards are used to assure that the components of a system, manufactured by different entities, will be able to connect as needed to fulfil the intended purpose.

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The final category of standards, those for testing and measurement, are intended to provide guidelines for how to test required performance, or how to measure performance, for specific materials, systems or assemblies. Application of these standards results in information on the acceptability (e.g. pass/fail) or the performance category (e.g. Class A, 1-hour) of a material, system or assembly, or provides data that can be used to determine acceptability or performance. Standards of this type can be developed through standards development organizations, by listing/approvals/certification bodies or by private entities. For example, ASTM develops a wide range of standards regarding material performance and how materials are to be tested. ASTM, however, does not conduct testing: this needs to be done by listing/approvals/certification entities, such as UL, Southwest Research Institute, or other such entity. In some cases, the listing/approvals/certification entity may develop their own testing standards as well. This is the case with UL. Finally, there may be specific standards developed and required by insurance companies. FMGlobal is a good example of this. FMGlobal provides certification and approval of products, much like UL, but more focused on industrial applications. When product is tested by a listing/approvals/certification entity, to an accepted standard, a product listing or certification can be issued. This generally comes with the stipulation that the product, system or assembly meets the test requirements under the specific test conditions. The product may then be labeled or marked (e.g. with a UL label or an FMGlobal label). This is similar in concept to obtaining a CE mark in the European system. As an example of how the system works, consider the approach to fire resistance rating in the International Building Code. First, the code requires that all buildings be classified in one of five construction types, which identify fire resistance ratings for different building elements. The International Building Code then goes on to require that the fire resistance ratings be determined in accordance with the test procedures set forth in specified ASTM or UL tests. If a manufacturer had a product for which a fire resistance rating is required, they could have the product tested at an acceptable listing/approvals/certification entity, such as UL or FMGlobal. If successful, a certification is provided, the product becomes “listed”, and may bear the appropriate indication (e.g. UL or FMGlobal label or marking). A listing of the certifications, which include product, system or assembly materials and construction, is available to designers and authorities as a means to assess whether the product meets the code requirements. As noted above, there is the option within the International Building Code, and within state building codes, to use “alternate methods or materials”. This can extend to required tests. Returning to the example of the fire resistance rating, the International Building Code allows alternate methods, which include calculations as specified in the code or engineering analysis based on a comparison to a design (or designs) having a fire resistance rating as determined by the test procedure set forth in specified ASTM or UL tests. In cases where a specific product does not have a UL or equivalent listing, or using an alternate approach as outlined above, it can be helpful to have

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Building Code development processes

the product evaluated for code compliance by an entity such as the International Code Council Evaluation Service, which undertakes technical evaluations specific to the issue of code compliance (e.g. does this method or material comply with the code). As such, if the evaluation confirms compliance, the evaluation report becomes a valuable tool for authorities and others. 9.3 Building Code development processes As noted above, a key aspect of the building regulatory process in the United States is that model building and fire codes are developed in the private sector for adoption, if desired, by state or local jurisdictions. As noted above, there are two primary model code development organizations in the United States: the International Code Council and the National Fire Protection Association (NFPA). While their processes are similar, it is helpful to understand some of the differences in approach and philosophy. 9.3.1 International Code Council The International Code Council develops construction and public safety codes through the governmental consensus process. The governmental consensus process leaves the final determination of code provisions in the hands of public safety officials who, with no vested financial interest, can legitimately represent the public interest. The International Code Council governmental consensus process meets the principles defined by the National Standards Strategy of 2000; OMB Circular A-119, Federal Participation in the Development and Use of Voluntary Consensus Standards and in Conformity Assessment Activities (1998). It complies with Public Law 104-113 National Technology Transfer and Advancement Act of 1995. The International Code Council governmental consensus process adheres to the following principles: Openness • • •

Participation in the development of the codes, including code hearings, is open to all at no cost. Anyone can submit a code change proposal or make a public comment. Code committees must consider all views before voting.

Transparency • •

Evidence of committee vote, with reason, must be documented. Final decisions are made in an open hearing by public safety officials.

Balance of interest •

Committee members represent general interests, user interests, producer

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A brief overview of the building regulatory system in the USA

• •

interests, or multiple interests. One-third of the committee’s members must be public safety officials. Committee members cannot vote on issues that are a conflict of interest. International Code Council membership is not a condition of committee membership.

Due process • • •

A code change proponent has the opportunity to rebut opponents and vice versa. Anyone who attends the hearing can testify. Committees are required to consider all views, objections and the cost impact of all code change proposals.

Appeals process • •

Anyone can appeal an action or inaction of the code committee. International Code Council renders its decision on the appeal based on whether due process was served.

Consensus • • •

Committee members vote to approve the code change, make modifications to it or vote against it. A simple majority from the committee decides the action of the proposed code change. International Code Council assembly action allows members to challenge the action of the committee.

The International Code Council process has three main objectives: 1. 2. 3.

The timely evaluation and recognition of technological developments pertaining to construction regulations. The open discussion of proposals by all parties desiring to participate. The final determination of Code text by officials representing code enforcement and regulatory agencies and by honorary members.

The International Code Council process takes about three years to complete from start to finish and includes the following steps: 1. 2. 3. 4. 5. 6. 148

code changes submitted code changes posted and cd distributed code development hearing public hearing results posted and cd distributed public comments sought on public hearing results public comments posted and cd distributed

Building Code development processes

7. 8.

final action hearing new edition published.

9.3.2 National Fire Protection Association In the NFPA standards development process, the Technical Committees and Panels serve as the principal consensus bodies responsible for developing and updating all NFPA codes and standards. Committees and Panels are appointed by the Standards Council and typically consist of no more than 30 voting members representing a balance of interests. NFPA membership is not required in order to participate on an NFPA Technical Committee, and appointment is based on such factors as technical expertise, professional standing, commitment to public safety, and the ability to bring to the table the point of view of a category of interested people or groups. Each Technical Committee is constituted so as to contain a balance of affected interests, with no more than one-third of the Committee from the same interest category. The Committee must reach a consensus in order to take action on an item. One of the most notable features about NFPA’s standards development process is that it is a full, open, consensus-based process. “Full consensus” means that anybody can participate and expect fair and equal treatment. The NFPA process encourages public participation in the development of its codes and standards. All NFPA codes and standards (also referred to here as NFPA “Standards”) are revised and updated every three to five years in revision cycles that begin twice each year and that normally take approximately two years to complete. Each revision cycle proceeds according to a published schedule that includes final dates for all major events in the process. An NFPA Standard is open for public input as soon as the current edition is published. The process contains four basic steps leading to the issuance of an NFPA Standard in the subsequent revision cycle: Step 1: Input stage • • • • • •

Input accepted from the public or other committees for consideration to develop the First Draft. Committee holds First Draft Meeting to revise Standard (23 weeks). Committee(s) with Correlating Committee (10 weeks). Committee ballots on First Draft (12 weeks). Committee(s) with Correlating Committee (11 weeks). Correlating Committee First Draft Meeting (9 weeks). Correlating Committee ballots on First Draft (5 weeks). First Draft Report posted.

Step 2: Comment stage •

Public Comments accepted on First Draft (10 weeks).

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A brief overview of the building regulatory system in the USA

•

• • • • •

If Standard does not receive Public Comments and the Committee does not wish to further revise the Standard, the Standard becomes a Consent Standard and is sent directly to the Standards Council for issuance (see Step 4). Committee holds Second Draft Meeting (21 weeks). Committee(s) with Correlating Committee (7 weeks). Committee ballots on Second Draft (11 weeks). Committee(s) with Correlating Committee (10 weeks). Correlating Committee First Draft Meeting (9 weeks). Correlating Committee ballots on First Draft (8 weeks). Second Draft Report posted.

Step 3: Association Technical Meeting • • • •

•

Notice of Intent to Make a Motion (NITMAM) accepted (5 weeks). NITMAMs are reviewed and valid motions are certified for presentation at the Association Technical Meeting. Consent Standard bypasses Association Technical Meeting and proceeds directly to the Standards Council for issuance. NFPA membership meets each June at the Association Technical Meeting and acts on Standards with “Certified Amending Motions” (certified NITMAMs). Committee(s) and Panel(s) vote on any successful amendments to the Technical Committee Reports made by the NFPA membership at the Association Technical Meeting.

Step 4: Council Appeals and Issuance of Standard •

•

Notification of intent to file an appeal to the Standards Council on Association action must be filed within 20 days of the Association Technical Meeting. Standards Council decides, based on all evidence, whether or not to issue the Standard or to take other action.

As one can see, the codes and standards development process is quite similar between the two organizations. The primary difference lies in those who are eligible to vote on “final” versions of a document. In the International Code Council system, only governmental members are eligible to vote. In the NFPA system, all paying members (who meet certain membership time requirements) are eligible to vote. A summary comparison of the International Code Council and NFPA systems is presented in Table 9.1 below (see references for details). 9.4 Structure of the International Building Code As noted above, the International Building Code is the primary model building code used in the United States. It is developed by International Code Council and

150

Structure of the International Building Code

Table 9.1 Comparison of International Code Council and NFPA Code development processes

Aspect

International Code Council

Type of Non-profit organization How the process Code Development Committees draft new works codes or standards, changes to codes or standard, review code change proposals from others, and recommend final wording to membership. Who can initiate Anyone – do not need to be a member. a code change proposal? Committee Minimum of 33.3% of committee must be Make-up regulators. Multiple interests are encouraged. Code Eight-step process over thee years. Codes development updated every three years. cycle Is cost impact Yes, has it as a requirement in the proposal considered? submittal stage.

NFPA Non-profit Technical Committees draft new codes or standards, changes to codes or standard, review code change proposals from others, and recommend final wording to membership. Anyone – do not need to be a member.

Hearings

Holds a public hearing. This meeting takes place in between the proposal and comments stages.

Who can vote?

At Public Hearing: All members in attendance for the public hearing.

No more than 33% of one interest. Multiple interests are required. Four-step process over 104 to 141 weeks. Codes updated every three to five years. Yes/no, does not make the cost impact a requirement, but the cost impact on the code change could affect how the committee rules on the proposal. Holds a hearing which only NFPA voting members at the Annual Technical Meeting can vote. This meeting takes place after the proposal and comments stages. At development stage: The Technical Committee

At Final Action Hearing: Governmental Member Representatives and Honorary Members in attendance

At Annual Meeting (Technical Session): Any NFPA member present for the vote on the proposal

made available to states and local jurisdictions for adoption into regulation (with or without modification). The International Building Code is a prescriptive document with more than 600 pages of requirements in 35 chapters, and including six codes published by International Code Council: • • • • • •

International Fuel Gas Code (2012), International Mechanical Code (2012), International Plumbing Code (2012), International Property Maintenance Code (2012), International Fire Code (2012), and International Energy Conservation Code (2012).

There is also and one published by NFPA, the National Electrical Code (2011). 151

A brief overview of the building regulatory system in the USA

Collectively these reflect several hundred additional pages of requirements, and several hundred reference standards, guidelines and codes of practice. One- and two-family residences are addressed separately from the International Building Code under the International Residential Code (2012). The scope of the International Building Code is as follows: The provisions of this code shall apply to the construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures. The intent of the International Building Code is stated as follows: The purpose of this code is to establish the minimum requirements to safeguard the public health, safety and general welfare through structural strength, means of egress facilities, stability, sanitation, adequate light and ventilation, energy conservation, and safety to life and property from fire and other hazards attributed to the built environment and to provide safety to firefighters and emergency responders during emergency operations. The structure of the International Building Code is as follows: • • • • • • • • • • • • • • •

Scope, administration, definitions: Chapters 1–2. Use/occupancy classification, special requirements, heights and areas, construction: Chapters 3–6. Fire provisions: Chapters 7–9. Means of egress and accessibility: Chapters 10–11. Interior environment and energy efficiency: Chapters 12–13. Exterior walls and roof assemblies: Chapters 14–15. Structural design, inspections, soils and foundations: Chapters 16–18. Materials (e.g. concrete, steel, wood, etc): Chapters 19–26. Electrical, mechanical and plumbing systems: Chapters 27–29. Elevators and escalators: Chapter 30. Special construction: Chapter 31. Encroachments into public right-of-way: Chapter 32. Safeguards during construction: Chapter 33. Existing structures: Chapter 34. Referenced standards: Chapter 35.

While generally a very prescriptive document, “performance” specifications are used as well. Prescriptive examples include such factors as maximum height and area based on building construction type, maximum travel distance to an exit,

152

Developments in support of performance-based building and fire regulations

and size and spacing of fasteners for structural systems. However, the International Building Code also provides “performance” specifications such as hourly ratings for fire resistance, hazard maps for determining load conditions, and equations for assessing allowable load combinations. The mix of “prescriptive” and “performance” specification varies by subject (e.g. loads and relationship for structural design can be considered performance, with egress requirements being only prescriptive). 9.5 Developments in support of performance-based building and fire regulations The approach to using model codes for building and fire regulation developed out of the desire to have more uniformity in building construction and safety regulation across the United States, even though individual states have the right to regulate building safety as they deem appropriate. From the 1920s until the early 1990s, there were nominally four model code organizations in the country writing codes that were largely adopted on a regional basis. While groups such as the American Institute of Architects and the National Association of Home Builders pushed for code uniformity (3),(24), other groups, including government agencies such as the Department of Housing and Urban Development and the National Bureau of Standards, were starting to promote a performance-based system through an effort called Operation Breakthrough (3). While there was interest in performance-based building codes at the time, the desire to consolidate the different model building codes into a common code for the United States dominated the activity through the 1980s. However, by the late 1980s and early 1990s, discussion was expanding within the United States’ building and fire communities on ways to streamline and reduce the level of building regulations without compromising the level of health and safety provided. This discussion was initiated for several reasons, including the aims of streamlining and reducing regulation, better incorporating innovative materials and methods into building design and construction, reducing building design, construction, and operational costs, and increasing international competitiveness. One approach proposed for addressing this wide range of issues was to transition from a prescriptive- to a performance-based building code. The concepts of performance-based design and performance-based regulations began to be widely discussed in the United States’ building and fire communities at a National Science Foundation conference in 1991, Firesafety Design in the 21st Century (25). This brought together 112 participants who provided perspectives of practising engineers, architects, the fire service, building officials, attorneys, researchers and academics. In addition to listening to presentations by key members of the building and fire communities, the conference attendees participated in breakout groups that focused on major issues. Through the breakout groups and summary discussion, the conference participants identified a number of important goals, barriers and strategies for fire safety design in the 21st century. A US national goal was formulated that “by the year 2000,

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A brief overview of the building regulatory system in the USA

the first generation of an entirely new concept in performance-based building codes be made available to engineers, architects and authorities having jurisdiction . . . in a credible and useful form”. The primary barrier to achieving this goal was identified as a lack of fire safety goals in building codes and standards. In the years following this conference, activities were undertaken to investigate the feasibility of performance-based codes, and the associated performance-based design methods, that would be needed to support such a system. This included activities in the fire engineering area (26),(27),(28) and the seismic engineering community (29), as well as in the model code groups. Efforts within the model code groups were facilitated by the formation of International Code Council and their negotiations with NFPA on development of a common set of model building and fire codes, and the subsequent breakdown in negotiations which led to International Code Council and NFPA each developing their own model codes. Given the confluence of each organization wanting to be seen as the leader for model code development and of the transition to performance-based building regulation in different parts of the world (26),(30), both International Code Council and NFPA embarked on development of a performance-based code. For the International Code Council, this resulted in the development of the ICC Performance Code for Buildings and Facilities (2012) and for NFPA it resulted in the performance option in NFPA 5000, Building Construction and Safety Code (2012) (the same approach is present in NFPA 101, Life Safety Code (2012). 9.5.1 International Code Council performance approach When the ICC Performance Code for Buildings and Facilities was being developed, one aim was to adopt the approach that had become common in other countries: the application of the Nordic Building Code Committee structure (33),(34) and development of goals, functional objectives, operative requirements, verification methods and acceptable solutions (35),(36),(37),(28),(38). This aim was achieved, and the general structure of the ICC Performance Code for Buildings and Facilities is illustrated in Figure 9.3. Another aim was to include aspects of the building code and the fire code into a single document. This was achieved by separating the ICC Performance Code for Buildings and Facilities into three primary sections: Part I – Administrative, Part II – Building, and Part III – Fire. While aiming to follow the Nordic Building Code Committee structure, it was also desired to introduce a way to address different levels of performance expected from buildings, given different risk characteristics of the occupants, building and hazards, and different events and magnitudes of events that buildings might face over their lifetimes. In doing this, an approach proposed within the seismic engineering community, which considered operational impact, facility importance and event magnitude (29) was adopted and adapted for use across a broader range of hazards (38),(39),(40). This is reflected in Figure 9.4 as the “Design Performance Levels” at the top of the diagram. In brief, the approach to “Design Performance Levels” consists of three major components: grouping of different building uses into four Performance

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Developments in support of performance-based building and fire regulations

9.3 ICC Performance Code for Buildings and Facilities structure

General administrative procedure particular to a performance code Chapters 1 and 2

Administrative Provisions

Provides guidance on design performance levels Chapter 3

Design Performance Levels Code

Objectives Topic-specific intent statements Chapters 4 through 22

Functional Statement Performance Requirements

Section 104 Acceptable Methods

Not in code

Prescriptive Codes

Authoritative Documents and Design Guides

Other Design Documents

Solution Performance Criteria

Measurable – example design load, heat flux

Verification

Testing, modeling, etc.

Documentation Solution

INCREASING LEVEL OF BUILDING PERFORMANCE

INCREASING MAGNITUDE OF EVENT

9.4 Maximum tolerable damage based on performance groups and design event magnitude

MAGNITUDE OF EVENT

PERFORMANCE GROUPS PG I

PG II

PG III

PG IV

VERY LARGE (very rare)

Severe

Severe

High

Moderate

LARGE (rare)

Severe

High

Moderate

Mild

MEDIUM (less frequent)

High

Moderate

Mild

Mild

SMALL (frequent)

Moderate

Mild

Mild

Mild

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A brief overview of the building regulatory system in the USA

Groups (PG), PG I–PG IV, which are based on factors such as risk to occupants, risk to those outside of the building, and importance to the community (economic, heritage, or other); defining different magnitudes of design events expected to impact on the building (Small to Very Large); and defining maximum levels of damage to be tolerated (Mild to Severe) as a function of structural stability, nonstructural damage, occupant hazards, overall extent of damage, and release of hazardous materials (38). The factors combine into a matrix of performance groups, design events, and levels of tolerable impacts, as illustrated in Figure 9.4. Conceptually, Performance Group I (PG I) consists of buildings with low risk to life or property, or for which a low level of hazards are present (e.g. no hazardous materials), and at the other end, PG IV consists of buildings or facilities that are highly important as they provide essential services (e.g. hospital expected to be operational after an earthquake) or present a high hazard. PG II and PG III consist of all other buildings, with division based on factors such as total number of occupants, occupant risk factors, etc. For any given design event magnitude, such as LARGE (e.g. large fire, large earthquake, etc), there is a maximum tolerable design damage (impact) level specified for the different PGs: “Severe” impact can be tolerated in buildings in PG I (e.g. a detached garage associated with a single family dwelling), no more than “High” impact can be tolerated in buildings in PG II (e.g. a small office building), no more than “Moderate” impact can be tolerated in buildings in PG III (e.g. a high-rise building or large assembly space), and no more than “Mild” impact can be tolerated in buildings in PG IV (hospital or other essential facility). The ICC Performance Code for Buildings and Facilities contains no prescriptive solutions: the International Building Code is deemed-to-comply with its performance requirements. 9.5.2 NFPA performance approach NFPA took a different approach to performance. While in concept the Nordic Building Code hierarchy is applied, and NFPA 5000Building Construction and Safety Code Building Construction and Safety Code (2012) includes goals, objectives, performance requirements and so forth, the document is predominantly prescriptive, with a “performance option” being presented as an alternative. In contrast to the International Code Council approach, a variety of “design scenarios” are provided for fire, structural and safety during building use. The NFPA 5000is not widely used in the United States, it is required by some federal government agencies, but not by many state or local jurisdictions. However, it should be noted that the “scenario” approach is used within NFPA 101, Life Safety Code, which is more widely used than NFPA 5000by fire protection engineers in structuring fire scenarios for analysis. 9.6 Summary The system in the United States is complex due to constitutional rights to regulate buildings existing at the state and local level, with no nationally-mandated building code or federal agency with building regulatory oversight. The system

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References

utilizes a set of model codes for major building function, along with hundreds of reference standards, which must be adopted into regulation at the state or local level. The primary model building code used as the basis for state and local building codes is the International Building Code published by the International Code Council. The International Building Code is principally a prescriptive document, although some performance criteria are used. Enforcement of the building code is primarily at the local level. The code development process for the International Code Council, and the other major model code organization, the National Fire Protection Association (NFPA), is presented. A discussion on directions toward performance is provided. Given the complexity of the building regulatory system, and the desire to have as common a system as practicable across the United States, the system remains primarily prescriptive, with performancebased design being undertaken by exception under the “alternate methods and materials” clause in the building code. Author Brian J. Meacham is Associate Professor, Department of Fire Protection Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts, United States. Much of this chapter is excerpted with permission from B.J. Meacham, A Process for Identifying, Characterizing, and Incorporating Risk Concepts into Performance-Based Building and Fire Regulation Development, Ph.D. Dissertation, Clark University, Worcester, MA, April 2000, all rights reserved. References (1) Lowi, T. (1988). “Liberal and Conservative Theories of Regulation,” in Bryner G.C. and Thompson. (2) Zimmerman, J.F. (1983). State-Local Relations: A Partnership Approach, Praeger, Westport, CT. (3) Field, C.G. and Rivkin, S.R. (1975). The Building Code Burden, Lexington Books, D.C. Heath and Co, Lexington, MA. (4) Burgess, P. (1998). An Acceptable Degree of Risk: A Study of Ohio’s Building Standards Law, A Report Prepared for the National Institute of Building Sciences, The Urban Center, Cleveland State College, Cleveland, OH. (6) Mandelker, D.R. and Netsch, D.C. (1977). State and Local Government in a Federal System: Cases and Materials, Bobbs-Merril Co. Inc, New York. (7) ICC (2007). Building Department Administration, International Code Council, Washington, DC. (17) Bukowski, R. (2002). “The Role of Standards in a Performance-Based Building Regulatory System,” Proceedings, 4 th International Conference on Performace-Based Codes and Fire Safety Design Methods, Society of Fire Protection Engineers, Bethesda, MD. (18) Hemenway, D. (1975). Industrywide Voluntary Product Standards, Ballinger Publishing Co., Cambridge, MA. (19) Cheit, R.E. (1990). Setting Safety Standards: Regulation in the Public and Private Sectors, University of California Press, Berkeley, CA (http://ark.cdlib.org/ark:/13030/ft8f59p27j/). (24) Liebing, R.W. (1987). Construction Regulations Handbook, John Wiley & Sons, Inc, NY.

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A brief overview of the building regulatory system in the USA

(25) Lucht, D.A., ed. (1991). Proceedings of the Conference on Fire Safety Design in the 21st Century, ISBN 1-881172-01-5, Worcester, MA. (26) Meacham, B.J. (1998). The Evolution of Performance-Based Codes and Fire Safety Design Methods, NIST GCR 98-763, NIST, Gaithersburg, MD. (27) Meacham, B.J. (1998). Concepts of a Performance-Based Building Regulatory System for the United States, GCR 98-762, NIST, Gaithersburg, MD. (28) Meacham, B.J. (1998). Assessment of the Technological Requirements for Realization of Performance-Based Fire Safety Design in the United States: Final Report, GCR 98-761, NIST, Gaithersburg, MD. (29) Hamburger, R.O., Court, A.B. and Soulages, J.R. (1995). “Vision 2000: A Framework for Performance-Based Engineering of Buildings”, Proceedings of the 64th Annual Convention, Structural Engineers Association of California, Whittier, CA, pp. 127–46. (30) Meacham, B.J., Moore, A., Bowen, R. and Traw, J. (2005). “Performance-Based Building Regulation: Current Situation and Future Needs,” Building Research and Information, Vol. 33, No. 1, pp. 91–106. (33) NKB (1976). Nordic Committee on Building Regulations (NKB), Programme of Work for the NKB, Report No. 28, Stockholm. (34) NKB (1978). Nordic Committee on Building Regulations (NKB), Structure for Building Regulations, Report No. 34, Stockholm. (35) Traw, J. and Tubbs, B. (1997). “Future Perspective of the U.S. Model Building Codes”, Proceedings of the 1996 International Conference on Performance-Based Codes and Fire Safety Design Methods, SFPE, Boston, MA, pp. 51–64. (36) Tubbs, B. (1998). “Status of the ICC’s Performance-Based Code Development, Proceedings of the 1998 Pacific Rim Conference and Second International Conference on Performance-Based Codes and Fire Safety Design Methods, ISBN 1-58001-011-3, ICBO and SFPE, Whittier, CA, pp. 195–204. (37) Tubbs, B. (1999). “Performance-Based Codes in the US: The International Code Council Perspective”, Proceedings of the International Convention on Global Building Model in the Next Millennium, Victoria Building Control Commission, Melbourne, Australia, pp. 16–23. (38) Meacham, B.J., ed. (2004). Performance-Based Building Design Concepts, ISBN 1-58001182-9, International Code Council, Falls Church, VA. (39) Meacham, B.J. (2000). A Process for Identifying, Characterizing, and Incorporating Risk Concepts into Performance-Based Building and Fire Regulation Development, Ph.D. Dissertation, Clark University, Worcester, MA, April 2000. (40) Meacham, B.J. (2000). “Incorporating Risk Concepts into Performance-Based Building and Fire Code Development”, in Lucht, D.A., ed., Proceedings of the Second Conference on Firesafety Design in the 21st Century, WPI and SFPE, Worcester, MA, 2000, pp. 115–29.

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Chapter 10

Legislation, codes of practice and standards in Hong Kong and mainland China W.K. Chow and X. Dong

In this chapter, the legislations, codes of practice and standards associated with building fire safety in Hong Kong will be briefly reviewed, along with an outline of the fire codes in mainland China. 10.1 Hong Kong The fire codes in the Special Administrative Regions of Hong Kong are basically prescriptive (1),(2). However, it has not been demonstrated that the existing codes are supported by systematic research with experimental justification. Yet many large-scale construction projects have been completed in both Hong Kong and mainland China. There are very tall buildings over 300 m high, atria with a space volume over 28,000 m3, underground railway stations built 40 m below ground and tunnels up to 30 km in big cities such as Shanghai, Guangzhou and Hong Kong. Buildings with green architectural features are also under construction, or in the planning phase. However, there have been serious fires including the 1996 Garley Building fire (3) in Hong Kong and others in mainland China (4) and fire safety provisions are very important and should be assessed carefully. Efforts have been made to review the local fire codes (1) earlier this century, but once again, no research papers supporting the code specifications (1) have been published to explain the concept, data and approach. 159

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Projects having difficulties in complying with the prescriptive codes in Hong Kong are allowed to follow a fire engineering approach (5),(6),(7),(8),(9). However, no clear acceptance criteria (1),(5), that are supported with systematic research have been established as in performance-based design of other countries (10),(11),(12),(13). 10.1.1 Prescriptive approach Hong Kong was previously a British colony (until 30 June 1997) and most of the fire codes followed the British system such as the BS 5588 (14), with modifications to satisfy local demands. Hong Kong’s fire codes (1),(2), which were developed decades (15),(16),(17) ago, are basically prescriptive. Passive building construction and active fire protection systems are handled by two departments under the Building Ordinance and Fire Services Ordinance. The Fire Safety Code on passive building construction has been effective since April 2012 (1), with the Buildings Department being in charge. The code review was monitored by a committee of fire officers, academics and representatives from the construction industry. The new Fire Safety Code combines and is updated from earlier fire codes: the Code of Practice for Fire Resisting Construction (16), the Code of Practice for Provisions of Means of Access for Firefighting and Rescue Purposes (15) and the Code of Practice for Provisions of Means of Escape in Case of Fire and Allied Requirements (17). All passive building design issues, such as fire resisting construction, means of escape and means of access, are included. This guarantees sufficient means of egress from the building and means of access for firefighting and rescue, while the building structure remains intact and fire spread will be prevented. Active fire protection system or fire services installation falls into the domain of the Fire Services Department. Detailed requirements and specifications are described in the Code of Practice for Minimum Fire Service Installations and Equipment and Inspection and Testing and Maintenance of Installations and Equipment (FSI code) (2). This first appeared in 1964, and more detailed specifications were listed in 1973. The code underwent significant revisions with the addition of many new items in 1987, and there were revisions again in 2005 and 2012. The code covers all fire services installations and equipment: fire alarm and detection systems; suppression systems, including sprinkler system, fire hydrants and hose reel system; air systems; and others such as emergency lighting and exit signs. These installations serve different purposes, including extinguishing, attacking, preventing, or limiting a fire; giving warnings; providing access to any premises for extinguishing, attacking, preventing or limiting a fire. Fire safety required for some special buildings with high occupant loading and/or with high amount of combustibles such as subway stations is also specified, such as the Guidelines on Formulation of Fire Safety Requirements for New Railway Infrastructures (18), which was released in January 2013.

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10.1.2 Submission of new projects After an authorized person submits a new building design to the Building Department, the department will check all fire aspects (1),(15),(16),(17) for approval, while the Fire Services Department (2) determines the requirements and installation of fire protection systems. The application process is shown in Figure 10.1. Fire resistance rating, previously known as fire resistance period, is a key factor in the local building fire safety code (1). The required fire resistance rating for elements of construction (19) is generally designated as 60, 120 or 240 minutes. Elements of means of egress and means of access are specified with adequate fire resistance rating. All liftwell enclosures should be separated from other parts of the building by a minimum of 120 minutes fire resistance rating. Any door to a liftwell wall should have a fire resistance rating of not less than 60 minutes in terms of integrity and insulation. Fire hydrants and hosereel systems must be installed in high-rise buildings and located within 30 m from any part of the building. The actuating point of the fire alarm system should be located at each hosereel point, and an audio warning device should also be installed. Sprinkler systems are required in most non-residential buildings, and they should be installed at every part of the building, including staircases and corridors. After the Garley Building fire, sprinkler systems are required in all non-residential buildings, even the aged high-rise commercial buildings. If there are difficulties to install a sprinkler system, for example insufficient space for sprinkler tank and pipeworks in existing buildings, a fallback plan (20) can be adopted (21). An automatic cut-off system should be installed to stop the mechanically induced air movement of a

10.1 Approval of fire safety provisions in Hong Kong

Passive (Buildings Department BD)

Active (Fire Services Department FSD)

New project

Design revised

PBC design following FS code

FSI design following FSI code

Submission to BD

Submission to FSD

Approved ?

Approved ?

Design revised Y

Y Opportunities for revision ?

FEA

N

N

Opportunities for revision ?

Y Fire hazard assessment by fire consultant

FEA ?

Fire Engineering Report considered by FSC, BD

Design rejected

FEA

N

N

FEA ? Y

Y

N

Y

Fire hazard assessment by fire consultant

N Design rejected

Fire Engineering Report considered by ACFSO, FSD Y

Y Opportunities for revision ?

N Design rejected

N Approved ?

Y

Y Project approved

N Approved ?

Opportunities for revision ?

N Design rejected

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ventilation system in the building. An independent emergency generator should also be provided. In the whole building and along all escape routes, emergency lighting and exit signs should be available. Artificial lighting is required to reach 30 lux at the floor level of the exit routes. In case of breakdown of lighting, emergency lighting should provide a minimum of 2 lux at floor level. These codes have demonstrated their strength for fire safety provisions in buildings with relatively simple structures usage. However, modern architectural design features have posed new challenges to fire safety design. Therefore, fire codes should be updated in order to cope with these rapid changes. This is particularly obvious for buildings of special hazards requiring individual design considerations. It is impossible to determine local safety provision without scientific fire research. 10.1.3 Fire engineering approach The Asian economies are growing rapidly, particularly in mainland China, Taiwan, Hong Kong, Japan, Korea, Singapore, Malaysia and Indonesia. Consequently, many large-scale construction projects are carried out in the region: very tall buildings over 300 m tall, tunnels as long as 30 km, subway stations built 40 m below the ground and shopping mall complexes with atria of more than 28,000 m3. Projects with difficulty in complying with the prescriptive fire codes in Hong Kong are allowed (1),(5),(8) to determine active fire engineering systems with some flexibility since 1987. One of the first projects was designing fire shutters in a big exhibition hall without partitioning the huge interior space. Later, a fire engineering approach was implemented for passive constructions (including fire resisting constructions, means of escape and means of access for firefighters) in 1998 (1),(5),(8). However, there are additional reasons for using performance-based design, as summarized in the literature: • • • • • • •

It allows innovative architectural design. Its application is more suitable for structures that are too tall above the ground, such as very tall buildings. Its usage goes well for subway stations as they are built too deep underground. It should be applied when hall spaces are huge. Performance-based design is preferred when travel distances are long. It can be used in structures with high occupant loadings. It is more feasible in tunnels with small cross-sectional areas.

Similar to other places as discussed in several performance-based design conferences (22), cost reduction is a strong driver for performance-based design. While cost reduction is a reasonable factor to consider in engineering solutions, it needs to be treated with care. Cost reduction cannot justify unsafe solutions, nor can it be recommended without an analysis of hazardous consequences. The

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pressure of cost reduction can result in unjustified fire scenarios in fire hazard assessment. Therefore, more attention should be paid to hidden fire problems in the approved fire engineering approach/performance-based design projects (7),(8). The big fires on Fa Yuen Street in 2011 (23),(24) had to be handled by a special fire-fighting plan. Additional problems will arise in fires that break out in huge halls with very long travel distance. It is difficult to adopt a new, engineering performance-based system at the moment (25). The fire safety provisions of such building projects have to be determined by performance-based design (1),(11),(13), if the objectives, acceptance criteria and approaches are derived through long-term research in fire science and engineering, as in other countries (26). In Hong Kong, only a fire engineering approach, which has demonstrated an equivalence to fire codes, has been implemented since 1998 (5),(8). In order to satisfy local authorities, numerous arguments have been made for new architectural features, particularly “green or sustainable” buildings since 2000 (6),(27),(28). Most of these new architectural features, such as double-skin façade (29), do not comply with the prescriptive fire safety codes (1),(2), and the codes cannot be updated to include these new buildings in a short time. There must be supporting research and development works when the requirements for the new buildings are decided. Many consultative meetings and open forums have to be held to convince the general public before implementation. Therefore, for those buildings having difficulty in complying with the prescriptive fire codes on passive building construction, the fire engineering approach (1),(5),(8) has been accepted by the Buildings Department since 1998. They might be regarded as performance-based design as they are equivalent to the prescriptive codes. The system is not yet an engineering performance-based fire code, such as New Zealand’s (26). Those codes (35) are only applicable to normal houses. A long-term consultancy study on reviewing the codes in Hong Kong was completed in 2012 and there are myriad arguments on the new code. Consequently, the code is under review, and a new technical committee has been set up to solve the identified problems. In 1998, the Building Department set up a Fire Safety Committee to assess the suitability of the application of the fire engineering approach in buildings which cannot follow the prescriptive fire codes on passive building construction. The Fire Services Department also established an advisory committee for the Fire Safety (Buildings) Ordinance and the Fire Safety (Commercial Premises) Ordinance in 2010 to assess and monitor the fire engineering approach on active systems. Experts were invited to be committee members. The Building Department has been keeping the minutes of the meetings, so the design criteria, the methods of approval and the fire safety objectives can be investigated when required, say after big fires in projects that went through fire engineering approach. The following items are assessed:

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• • • •

Fire safety objectives and acceptance criteria. Design parameters. Characterization of buildings and the occupants. Identification of potential fire hazard scenarios and their possible consequences. Assessment against the safety criteria.

•

10.1.4 Hidden problems More attention needs to be paid to other hidden fire problems, particularly in projects which went through performance-based design, or fire engineering approach since 1998 (1),(5),(9). Performance-based design was applied to many of these projects to reduce the cost. The associated fire engineering approach reports without justification on the assumed fire scenarios though experiments should be monitored carefully. Below are common issues that require special attention, some of which relate to performance-based design/fire engineering: 1. Crowded shopping malls, particularly those linked to subway stations, or with large amount of combustibles during festivals. For example, the risks are higher if a tall plastic tree is placed in the atrium of several storeys high (30). 2. Crowded subway stations without sprinkler coverage which get long Available Safe Egress Time (ASET) for evacuation by using low design fires. No data on human behaviour of local citizens was included in the estimation of the Required Safe Egress Time (RSET). In reality, ASET might only be slightly longer than RSET as pointed out recently (31). 3. Open kitchens without full coverage by fire suppressions system in small residential flats in tall buildings (32). Again, ASET are slightly longer than RSET in some cases. 4. Crowded supermarkets packed with large amount of goods during festivals. The upper limit on fire load density of 1135 MJm-2 should be kept (2),(33). 5. Long exit distance protected only by the provision of an emergency evacuation passage in subway tunnels. 6. Eevacuation paths in very tall buildings, which are only determined by codes for buildings of normal heights. 7. Long vehicular tunnels which use low design fires (34). Burning a heavy goods vehicle can give heat release rate over 200 MW, but the values are below 5 MW in the common design. 8. The use of improper engineering formulas in fire resistant partitions with low fire resistance period, for example only the metal board of the partition is taken into account in the estimation of thermal radiation heat flux (7), but not the fire gases. 9. Smoke management system design in tilted tunnels (35), particularly the ones with barriers assuming scenarios without in-depth experimental justification (36).

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10. The risks of post-flashover fire in buildings with glass façade were raised several years ago (37). It is possible for the glass system with window panes, frames or accessories to achieve acoustic effect or relieving wind pressure in rainstorms to prevent water leakage, to break into pieces (38),(39) to give big fires involving the whole building. The fire safety management (40) also needs to be worked out carefully in the high risk places listed above. In some countries, buildings with performancebased design/fire engineering approach approvals are required to assign at least two safety staff on each level 24 hours a day. 10.2 Codes in mainland China Following the Fire Control Law of the People’s Republic of China (41), an effective fire safety management approach was adopted. The central government exerts leadership; individual departments are responsible for fire safety; concerned units bear full liabilities and individuals are actively involved. All parties are expected to follow fundamental objectives to prevent fires and reduce the consequent damages, strengthen emergency rescue, and protect lives and property. A fire safety network that involves every level is intended to be established so as to ensure economic and social development. The fire safety management is based on prevention. The State Council is the leading body of all fire safety policies; regional governments execute them. The Ministry of Public Security monitors and manages the implementation of fire safety policies at central level, and the local Public Security teams at regional level. Each party bears the following responsibilities: • •

•

•

The State Council promulgates the country’s fire services policies. Regional governments are responsible for fire-fighting and leading their administrative area. Regional governments should include fire-fighting and control following guidelines instructed in the national economic and social development plans. Different levels of regional governments, departments, organizations, enterprises, corporations, etc, should organize educational programmes on fire prevention to raise citizens’ awareness. The Ministry of Public Security supervises, implements and manages all national fire safety policies. All fire departments of the local governments above the county level should supervise, control and manage fire prevention measures (except those related to military, underground mines, nuclear power plants, offshore oil and gas facilities, forests and grasslands) within their administrative region. Other relevant departments of the regional government above the county level should carry out precautionary measures within their scope of duties. Every unit and individual should ensure fire safety, protect fire-fighting facilities, prevent the outbreak of fire, and report fire. Every unit and adult should participate in organized fire-fighting activities.

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•

The country encourages and supports scientific fire research and innovative technology; it promotes the use of advanced fire technology, emergency rescue technology and equipment; it also supports the general public to take appropriate action on fire safety.

10.2.1 Fire prevention Regional governments at various levels should formulate and implement fire prevention plan. The fire safety design of construction projects must comply with the national fire protection technical standards. All parties, including constructors, designers, building operation personnel and supervisors, should follow the national legal system. Construction permits should not be issued to projects which have not been audited or fail the assessment. The construction should not commence without a permit. Also, the construction must be stopped if it does not fulfil the requirement during surprise inspections. Fire safety provision checks and record keeping should be mandatory after the completion of the construction project. Fire safety checks must be performed before the opening of public gathering places and facilities. Departments, organizations, enterprises, corporations, etc should fulfil and bear the legal responsibilities. Quality of firefighting equipment must meet the national standards. If there is no national standard on special products, the trade standards need to be met. Fire-fighting equipment that is untested and forbidden must not be produced, sold or used. The fire behavior of all the building components, building materials, and decorative materials must meet the fire safety requirements. The interior finish of places with high occupant loadings should conform to the national fire technology standard, which requires the use of flame retardant or incombustible materials. For tubing and piping, their installation, use and design have to conform to the national fire technology standards and management regulations, so do the maintenance and testing of the electrical products and gas appliances. The fire-fighting equipment and devices must not be damaged, misappropriated, or dismantled without approval. It is forbidden to bury, occupy or block fire hydrants. The fire prevention space must not be occupied. It is also prohibited to occupy, block or close escape routes, fire exits, and passageways for fire engines. 10.2.2 Fire protection organizations Regional governments at all levels should establish various forms of fire protection organizations, enhance the training of fire-fighting personnel, increase the capability of fire prevention and suppression, and set up emergency rescue forces according to the demands of the economic and social development. Regional governments above the county level should establish a public security and fire-fighting team, and a specialized fire-fighting team in accordance with the state regulations; they should also provide adequate fire-fighting equipment following the national standards. Governments of villages and towns should

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Codes in mainland China

establish a public security and fire-fighting team, and a voluntary fire-fighting team to undertake fire-fighting and rescue. The public security and fire-fighting team, and the specialized fire-fighting team should bear the responsibilities of emergency rescue in major disasters or accidents according to the state regulations. Nuclear facilities, large-scale power plants, civil airports, main ports, large factories which manufacture and store dangerous goods such as inflammables and explosives, and bulk warehouses which store inflammable goods should establish specialized fire-fighting teams. Departments, organizations, enterprises, corporations as well as village and resident committees should set up different organizations, such as a voluntary fire-fighting team. 10.2.3 Fire-fighting and rescue Regional governments above the county level should formulate contingency plans and emergency reaction and response mechanisms. Regarding the characteristics of different types of fires and disasters, they should provide adequate manpower and equipment for fire-fighting and rescue. The public security fire services departments should assume leadership among the organizations and take the command of real-time firefighting and rescue strategies of major fires; they should also carry out fire investigations and report the loss and damage caused after fires. 10.2.4 Supervision and inspection Different levels of regional governments should supervise and inspect the implementation of fire safety measures regularly. The public security organizations and the fire department should supervise and examine the departments, organizations, enterprises, corporations, etc on whether they comply with the law and regulations on fire safety. Relevant units or individuals should try to eliminate the hidden danger of fire immediately, should such potential danger be found. If such problem cannot be eliminated on time, the public security organization and the fire department should restrict access to such locations. If the fire safety provisions and public fire facilities do not satisfy the fire safety requirements or have serious potential fire hazard, the regional governments should instruct relevant departments and units to rectify the problem. 10.2.5 Ordinances and regulations There are over 20 ordinances and regulations, and more than 60 regional fire regulations have been passed in China. The basic Fire Control Law of the People’s Republic of China was implemented on 1 September 1998. To keep pace with the rapid social and economic developments, the revised version has been effective since 1 May 2008. Besides the state regulations, the People’s Congress of provinces, autonomous regions and municipalities should formulate their regional

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regulations based on the Fire Control Law of the People’s Republic of China. However, they should also take the local conditions into account. Examples include the Fire Protection Rules of Jiangsu Province and Fire Protection Rules of Tianjin, etc. In recent years, the Ministry of Public Security has issued a number of sectoral regulations to supplement the Fire Control Law of the People’s Republic of China, such as the Management regulations on supervisions and verification of fire prevention and control for building projects, Investigation regulations of fire accident, Supervision and inspection regulations of fire protection, Fire protection and safety management regulation for departments, organizations, enterprises and corporations and Management regulations on supervisions and verification of fire products. 10.2.6 Technical standards The National Technical Committee on Fire Protection of Standardization Administration of China (SAC/TC113) is responsible for enforcing the fire professional technical standards in mainland China. This committee, which is under the Standardization Administration of the People’s Republic of China (SAC), is responsible for formulating and revising all kinds of fire technical standards. Every fire technical standard should be examined and approved by the SAC/ TC113 first, and then submitted to the SAC or the technical supervision committee of the Ministry of Public Security. After the approval of SAC or the technical supervision committee of the Ministry of Public Security, the standard will be promulgated as the National Standard of the People’s Republic of China (GB) or the industry standard (GA). There are 14 sub-committees under the National Technical Committee on Fire Protection of Standardization Administration of China (SAC/TC113), which are in charge of the centralized management of professional technical standards of fire. The Fire Department of the Ministry of Public Security formulates the National Standard of the People’s Republic of China (GB) on construction engineering, while the General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China and Ministry of Construction develops and implements the standards together. Some important standards include Code for Design of Building Fire Protection, Code for Fire Protection Design of Tall Buildings, Code for Fire Prevention in Design of Interior Decoration of Buildings, etc. There are also some special design standards formulated by the Fire Department of the Ministry of Public Security and relevant parties, such as the Fire Protection Code of Petro-Chemical Enterprise Design and Design Code for Protection of Structures against Lightning. The details are given in (42),(43),(44),(45),(46),(47),(48). Whenever there are difficulties in complying with the Chinese Regulations, performance-based design can be adopted. Fire hazard of these buildings will be assessed. Appropriate fire safety provisions will be designed specifically. The buildings will be of the same safety level as required in the prescriptive codes, without defying the operational requirements. A fire safety evaluation report on performance-based design must be submitted to the Experts Committee. A series of meetings will be held to evaluate

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the designs under the direction of the Fire Authority. Fire safety requirements must be approved by the Fire Authority and the experts appointed. 10.2.7 Acceptance criteria In the fire engineering approach (31), it is important to work out the acceptance criteria for discussion with the authorities. The examples of acceptance criteria are: • • • • • • • • • •

•

Evacuation will ensure rapid movement of people away from the fire and minimise perturbations in the normal operation of the buildings. Occupant numbers will be estimated properly. Travel distances will be around 60 m. Means of escape have to be designed by fire engineering technique if prescriptive codes are not followed. Evacuees will go to a relatively safe place before reaching tenable limits. Smoke clear layer heights will be maintained above 2.1 m in open areas. Fire size will be based on sprinkler activation times, or limited by fire load. The cabin concept will be adopted for retail spaces connected to the concourse areas of public transport terminals. The computational fluid dynamics software will be used in various areas of the building. Fire and smoke spread through large open areas will be controlled with smoke reservoirs and other control devices, rather than solid fire resistant construction. Fire resistance of structural elements will be calculated by heat transfer theory.

Acceptance criteria commonly used for assessing the design and the rationale behind are listed in Table 10.1.

Table 10.1 Acceptance criteria specified in China

Criteria on

Tenability limit

Hot layer height in open concourse 2.1 m. When layer falls below this height, optical areas density and temperature become important. Thermal radiation 2.5 kWm–2 for occupants, 4.5 kWm–2 for fire-fighters Optical density (visibility) 0.1 m–1, (10 m), when layer falls below 2.1 m. Egress time 8-minute maximum queuing in congested conditions. 8-minute movement to place of safety in emergency, plus occupants must be able to egress without exposure to untenable conditions. Temperature for occupants moving 60°C for 30 minutes, when layer falls below through smoke 2.1 m.

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With occupants, tenability is lost once the following occur: • •

The smoke layer falls below 2.1 m above the finished floor level; temperatures exceed 60{degree}C or visibility falls below 10 m. The smoke layer hovers above 2.1 m; the hot layer releases over 2.5 kWm–2 of radiation to occupants.

To cope with the new architectural design features, in addition to updating the prescriptive codes, performance-based design should be established. There are many problems in the assessment of fire safety design based on fire engineering approach, and it might be easier to follow the updated prescriptive codes. Well-planned and long-term investigations need to be carried out before reaching the decision whether to stick to the updated prescriptive codes or switch to performance-based design. This should also be a “life-long” research project for upgrading the code to solve new problems. The following should be watched: •

•

• •

Fire safety provisions, including passive and active fire safety measures, will be better than the ones listed in the older versions of prescriptive codes (15),(16),(17). The defects of the current regulations can be pointed out and updated. The mandatory installation of sprinkler heads in high headroom atria and escape staircases are obvious examples. This is similar to imposing the local speed limit of 50km per hour in highways outside downtown areas, which almost all drivers ignore, which means that those drivers who follow the code and drive slower than the limit may be at risk. The selection of fire safety provisions will be more flexible, making it easier to satisfy different building requirements and uses. The reliability of fire safety provision will be supported by scientific analysis and engineering judgment.

Of course, there are good reasons (49) for keeping the prescriptive codes with active development: • • • •

It is easier to be implemented by the authority. Officers are well-trained to enforce the codes. The codes have been developed for many years and professionals are familiar with the requirements. The codes are more precise than performance-based design, making it easier to follow. For performance-based design, even the terms “goals” and “objectives” (12) have to be distinguished.

10.3 Conclusion Reviews of the fire codes in mainland China and Hong Kong have been published in different publications, and the principal author (6),(7),(8),(9),(50),

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Conclusion

(51),(52),(53),(54) was involved in some of them. The general characteristics of buildings in China were summarized (54). There are proposals on moving to engineering performance-based fire codes from the current prescriptive fire codes system, as in other areas in building including structural codes, wind loading codes, ventilation codes and engineering codes (25). There are many problems in the implementation of engineering performance-based fire codes, as raised (47) years ago. First, there must be systematic research on the fire safety objectives, acceptance criteria, engineering tools for hazard assessment, statistical fire records, verification methods and, more importantly, training of engineering professionals. It will take decades to gather the relevant information for very tall buildings, long tunnels, deep underground stations, large halls and buildings with green architectural features through long-term research. Moreover, there has been insufficient research funding (25). On the other hand, another key problem is that it would take a long time for officials to familiarize themselves with the system. Performance-based design with a clear requirement of prescriptive data might be more favourable. However, research is still very limited in Hong Kong and mainland China. Therefore, Hong Kong adopts the fire engineering approach, ensuring that fire safety provisions are equivalent to those required in prescriptive codes, as shown in Figure 10.2.

Engineering Performance-Based Fire Code EPBFC • • • •

Very few professionals able to do this. No systematic research. Takes time for transfer to this code system. High compensation cost of big fires, if occurred.

Performance-Based Design PBD • •

With clear supplementary data. Acceptance criteria are clear.

Fire Engineering Approach FEA • • •

Demonstrating equivalence to prescriptive code. No clear data. Case-by-case study.

Prescriptive Code

10.2 The four fire code systems (9)

• • • •

Big professionals doing this all over the world. Easier to implement. Professionals are safeguarded if everything complied with the code. Applicable only to traditional buildings.

171

Legislation, codes of practice and standards in Hong Kong and mainland China

References (1) Code of Practice for Fire Safety in Buildings 2012, Buildings Department, The Hong Kong Special Administrative Region, Draft version released for public consultation in September 2011, Implemented April (2012). (2) Codes of Practice for Minimum Fire Service Installations and Equipment and Inspection Testing and Maintenance of Installation and Equipment, Fire Services Department, Hong Kong Special Administration Region, China (2012). (3) South China Morning Post, Hong Kong, 21 November (1996). (4) South China Morning Post, “Blaze guts hotel at CCTV’s new 5b yuan complex”, 10 February (2009). (5) PNAP 204 Guide to Fire Engineering Approach, Practice Note for Authorized Persons and Registered Structural Engineers, Buildings Department, Hong Kong Special Administrative Region, March (1998). (6) Chow W.K. (2003) “Fire safety in green or sustainable buildings: Application of the fire engineering approach in Hong Kong”, Architectural Science Review, 46(3), 297–303. (7) Chow W.K. (2011) “Performance-based design on fire safety provisions in Hong Kong”, Invited speech, 2011 SFPE Annual Meeting: Professional Development Conference and Exposition, 24–25 October 2011, Portland, OR, USA. (8) Chow W.K. (2012) “Experience on implementing performance-based design in Hong Kong”, Welcome speech, the 9th Asia-Oceania Symposium on Fire Science and Technology, 17–20 October 2012, Hefei, China. (9) Chow W.K. (January 2013) “The four possible fire code systems”, Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong,. Available at: http://www.bse.polyu.edu.hk/researchCentre/Fire_Engineering/Hot_Issues.html>. (10) Hadjisophocleous G.V., Benichou N. and Tamim A.S. (1998) “Literature review of performance-based fire codes and design environment”, Journal of Fire Protection Engineering, 9(1), 12–40. (11) The SFPE Engineering Guide to Performance-Based Fire Protection Analysis and Design of Buildings, Society of Fire Protection Engineers and National Fire Protection Association, Quincy, Massachusetts, USA (2000). (12) NFPA (2003), NFPA 5000. Building and Construction Safety Codes, National Fire Protection Association, Quincy, MA, USA. (13) CIBSE (2010), CIBSE Guide E: Fire Engineering. The Chartered Institution of Building Services Engineers, London, UK. (14) BSI (2004) BS 5588, Fire Precautions in the Design, Construction and Use of Buildings. Access and Facilities for Fire-fighting, British Standards Institution, UK. (15) Buildings Department (1995) Code of Practice for Provisions of Means of Access for Firefighting and Rescue Purposes, Hong Kong. (16) Buildings Department (1996a), Code of Practice for Fire Resisting Construction, Hong Kong. (17) Buildings Department (1996b), Code of Practice for Provisions of Means of Escape in case of Fire and Allied Requirements, Hong Kong. (18) Fire Services Department, Guidelines on Formulation of Fire Safety Requirements for New Railway Infrastructures, Hong Kong Special Administrative Region, January 2013. (19) BS 476-22: 1987. Fire tests on building materials and constructions – Part 22: Methods for the determination of the fire-resistance of non-loadbearing elements of construction. London: British Standards Institution.

172

References

(20) Chow W.K. (2007) “On the fire safety requirements for existing old buildings”, International Journal on Engineering Performance-Based Fire Codes, 9(1), 31–7. (21) Fire Safety (Buildings) Ordinance Chapter 572, Laws of Hong Kong and its sub-leg Regulations, Hong Kong Special Administrative Region (2002). (22) Proceedings of Fire Safety Asia Conference (FiSAC) 2011, Suntec, Singapore, 12– 14 October 2011. (23) South China Morning Post, “An accident just waiting to happen”, 1 December (2011). (24) Chow W.K. (2012) “Large fire in Fa Yuen Street”, in G. Rein (ed.), International Association for Fire Safety Science Newsletter No. 32, p. 13, April (2012). (25) Torero, J. “Structures in fire or fires in structures: What do we need to know to achieve innovative fire safety”, International Fire Conference & Exhibition Malaysia (IFCEM 2012), 20–21 November 2012, Kuala Lumpur, Malaysia (2012). (26) Fleischmann, C., CPD lecture on “Performance-based design in New Zealand and the new verification method”, Organized by Research Centre for Fire Engineering, Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, 30 April and 2 May (2012). (27) Chow W.K. and Chow C.L. (2003) Green influences. Fire Prevention & Fire Engineers Journal, September, pp. 34–5. (28) Chow W.K. and Chow C.L. (2004) Fire safety concern on building design for reducing solar heat gain. 3rd China-Japan-US Symposium on Structural Health Monitoring and Control and 4th Chinese National Conference on Structural Control, Dalian University of Technology, Dalian, China, 13–16 October 2004, edited by Hongnan Li, Hui Li and Guoxin Wang, p. 150. (29) Chow C.L. (2013) “Full-scale burning tests on double-skin façade fires”, Fire and Materials, 37(1), 17–34. (30) Gregory C.H. Lo (2011) CPD lecture on “Fire Engineering in Hong Kong”, Organised by Research Centre for Fire Engineering, Department of Building Services Engineering, The Hong Kong Polytechnic University, 15 July (201). (31) Chow W.K. (2011) “Six points to note in applying timeline analysis in performance-based design for fire safety provisions in the Far East”, International Journal on Engineering Performance-Based Fire Codes, 10(1), 1–5. (32) Chow W.K. (2011) “Open kitchen fires in tall residential buildings”, CPD lecture organised by Research Centre for Fire Engineering, Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, 5 March (2011). (33) Chow W.K. (1989) “Fire Services Department Circular Letter No. 13/88: A comment”, The Hong Kong Engineer, November, p. 19. (34) Chow W.K. “Several points to note in performance-based design for fire safety provisions in Hong Kong”, The National Symposium on Fire Safety Science and Engineering, 14–16 October 2010, Beijing, China (2010). (35) Chow W.K., Wong K.Y. and Chung W.Y. (2010) “Longitudinal ventilation for smoke control in a tilted tunnel by scale modeling”, Tunnelling and Underground Space Technology, 25(2), 122–8. (36) Anny K.Y. Ip and Luo, M.C. (2005) “Smoke control in pedestrian subway”, Proceedings of the Hubei–Hong Kong Joint Symposium 2005, 30 June–3 July 2005, Wuhan, Hubei, China, pp. 70–9 (2005). (37) Chow W.K. (2008) Correspondences with TVB reporter on possible hazards in building glass facade fires, February. (38) Chow C.L., Chow W.K., Han S.S. and So Andrew K.W. (2006–07) “Vertical air temperature profiles in a single skin glass façade with a ‘Jumping Fire’ scenario”, Journal of Applied Fire Science, 17(2), 105–29. 173

Legislation, codes of practice and standards in Hong Kong and mainland China

(39) Chow C.L. and Chow W.K. (2010) “Experimental studies on fire spread over glass façade”, ASME 2010 International Mechanical Engineering Congress and Exposition, IMECE2010, 12–18 November 2010, Vancouver, British Columbia, Canada. (40) Lui Gigi C.H. and Chow W.K. (2000) “A demonstration on working out fire safety management schemes for existing karaoke establishments in Hong Kong”, International Journal on Engineering Performance-Based Fire Codes, 2(3), 104–23 (41) Chow W.K. (1999), “A Preliminary Discussion on Engineering Performance-Based Fire Codes in the Hong Kong Special Administrative Region”, International Journal on Engineering Performance-Based Fire Codes 1(1), 1–10. “Fire Control Law of the People’s Republic of China” http://www.mps.gov.cn/n16/n1282/n3493/n3763/n4198/1651320.html>. (42) Tianjin Fire Research Institute of Ministry of Public Security is in charge of specifying the National Standard of the People’s Republic of China (GB) “Code for design of building fire protection”. 天津市南開區衛津南路110號 公安部天津消防研 究所 規範研究室 (43) Sichuan Fire Research Institute of Ministry of Public Security is in charge of specifying the National Standard of the People’s Republic of China (GB) “Code for Fire Protection Design of Tall Buildings”. 四川省都江堰市外北街266號 公安部四川 消防研究所 規範研究室 (44) The 4th Engineer Design and Research Institute of General Staff Department is in charge of specifying the National Standard of the People’s Republic of China (GB) “Code for Fire Protection Design of Civil Air Defense Works”. 北京市太平路24號 總參工程兵第四設計研究院 國家標準《人民防空工程設計防火規範》管 理組. (45) Tianjin Fire Research Institute of Ministry of Public Security is in charge of specifying the National Standard of the People’s Republic of China (GB) “Code for design of Sprinkler System”. 天津市南開區衛津南路110號 公安部天津消防研究所 規範研究室 (46) Shenyang Fire Research Institute of Ministry of Public Security is in charge of specifying the National Standard of the People’s Republic of China (GB) “Code for Design of Automatic Fire Alarm System”. 遼寧省瀋陽市皇姑區蒲河街七號 公 安部瀋陽消防科學研究所 國家標準《火災自動報警系統設計規範》管理 組 (47) Shanghai Fire Research Institute of Ministry of Public Security is in charge of specifying the National Standard of the People’s Republic of China (GB) “Code for Design of extinguisher in buildings”. 上海市中山南二路601號 公安部上海消 防研究所 國家標準《建築滅火器配置設計規範》管理組. (48) Institute of Building Fire Research from China Academy of Building Research is in charge of specifying the National Standard of the People’s Republic of China (GB) “Code for Fire Prevention in Design of Interior Decoration of Buildings”. 北京安 外北三環東路30號 中國建築科學研究院防火所 國家標準《建築內部裝修 設計規範》管理組. (49) Kong Kenny S.M. and Chow W.K. (2000) Possibility of using engineering performance-based fire codes for higher education institutes. One-day Symposium on Advances in Building Services, Hong Kong Institution of Engineers, 21 November 2000, Kowloon Shangri-la Hotel, Hong Kong – Paper presented. (50) Fan W.C., Huo R., Yao B. and Chow W.K. (2001) “A brief review on active fire protection engineering systems in China”, Journal of Applied Fire Science, 10(4), 329–42. (51) Hung W.Y. and Chow W.K. (2001) “Review on fire regulations for new high-rise

174

References

commercial buildings in Hong Kong and a brief comparison with those in overseas”, International Journal on Engineering Performance-Based Fire Codes, 3(1), 25–51. (52) Chow W.K. and Lingcao Xia (2005–06)(FCHKChina3) “Building fire codes and performance-based design in China: Mainland and Hong Kong”, Journal of Applied Fire Science, 14(3), 223–38. (53) Chow W.K., Hu L.H. and Yang R.X. (2006)(RevChinaCode2) “A preliminary review on building fire codes and application procedure for new projects in China”, International Journal on Engineering Performance-Based Fire Codes, 8(3), 88–98. (54) Liu D.K., Lin M. and Chow W.K. (2005) “A general overview on the building constructions in China”, International Journal on Architectural Science, 6(4), 144–67.

175

Glossary of Fire Terms

acceptability: the extent to which the fire safety meets that deemed by society to be necessary, this may be expressed through legislation and influenced by the frequency of disasters. active containment: measures to contain the spread of fire which require the operation of some form of mechanical device (e.g. the operation of smoke vents or the release of fire shutters). addressable system: a comprehension/analysis system which compares the present situation with data stored in the system’s memory, to derive more than just fault and fire signals from the detectors, and to permit the precise location of the fire to be established. alternating sprinkler system: a sprinkler system which can be changed from “wet” operation in summer to “dry” operation in winter. appraisal/assessment: an estimate of the fire risks and fire precautions within a building. audit: an examination of the appraisal/assessment to check for accuracy in the estimation of fire risks, and the appropriateness and implementation of the fire precautions. auto-suppression: fire extinguishing systems which activate automatically on detecting a fire. bridgeheads: intended safe bases for firefighters attempting to tackle a fire within the building, served by protected lifts and adjacent to rising mains. burning brands: flaming debris carried by convection currents from buildings on fire. combustibility: the ease with which a material will burn when subjected to heat from an already existing fire. combustion: exothermic reaction of a combustible substance with an oxidiser. communication: the fire safety tactic of ensuring that if ignition occurs, the occupants are informed and any active fires safety systems are initiated. compartmentation: the technique of dividing a building into a number of compartments or sub-compartments. compartments: fire and smoke tight areas into which a building can be divided to contain fire growth and limit travel distance, offering at least 60 minutes resistance. 176

Glossary of Fire Terms

compartment floor: a fire-resisting floor used to separate one fire compartment from another and having a minimum period of resistance of 60 minutes. compartment wall: a fire-resisting wall used to separate one fire compartment from another and having a minimum period of resistance of 60 minutes. conduction: the transfer of heat by direct physical contact between solids. containment: the fire safety tactic of ensuring that the fire is contained to the smallest possible area, limiting the amount of property likely to be damaged and the threat to life safety. convection: the transfer of heat by the movement of the medium in liquids and gases. conventional system: a comprehension/analysis system where it is only possible to establish fault or fire signals from the detectors. diffusion flames: flames from combustion, where the rate of burning is determined by the rate of mixing of flammable vapours from a solid or liquid fuel and oxygen. dry rising main: a rising main normally kept empty of water, but to which the fire service can supply water at ground level in the event of a fire. dry sprinkler system: a sprinkler system where the majority of pipework is air filled until it is triggered. egress: direct escape to the outside. emergency lighting: lighting provided by standby generators on the failure of the mains supply. envelope protection: the limitation of the threat posed by a fire to adjoining properties and to people outside the building, and the threat posed by a fire in an adjoining property. equivalency: the provision of the same level of fire safety by different combinations of fire safety measures. escape: the fire safety tactic of ensuring that the occupants of the building and the surrounding areas are able to move to places of safety before they are threatened by heat and smoke. escape lighting: lighting provided on the failure of the normal lighting circuits by self-contained fittings. extinguishment: the fire safety tactic of ensuring that the fire can be extinguished quickly and with minimum consequential damage to the building. final exit: the termination of an escape route from a building giving direct access to a place of safety outside the building. fire: 1 – self-supporting combustion characterised by the emission of heat and effluent often accompanied by flame and/or glowing combustion. 2 – combustion spreading uncontrolled in time or space. fire door: a door or shutter provided for the passage of persons, air or objects which, together with its frame and furniture as installed in a building, is intended when closed, to resist the passage of fire and/or gaseous products of combustion and is capable of meeting specified performance criteria to those ends.

177

Glossary of Fire Terms

fire engineering: design which considers the building as a complex system, and fire safety as one of the many inter-related sub-systems which can be achieved through a variety of equivalent strategies. fire growth curve: the relationship between the time from ignition and the size of the fire. fire hazard: the potential for injury and/or damage from fire. fire load: the quantity of heat which could be released by the complete combustion of all the combustible materials in a volume, including the facings of all bonding surfaces. fire point: the minimum temperature at which material ignites and continues to burn for a specified time after a standardised small flame has been applied to its surface under specified conditions. fire precautions: measures which can be taken to reduce the likelihood of ignition occurring and/or mitigate the consequences should ignition occur, including the fire safety tactics of prevention, communication, escape, containment and extinguishment. fire propagation: the degree to which a material will contribute to the spread of a fire through heat release, when it is itself heated. fire protection: measures to limit the effects of fire, including the fire safety tactics of communication, escape, containment and extinguishment. fire resistance: the ability of an item to fulfil for a stated period of time the required stability and/or integrity, and/or thermal insulation, and/or other expected duty specified in a standard fire resistance test. fire risk: the product of: – probability of occurrence of a fire to be expected in a given state, and – consequence or extent of damage to be expected on occurrence of a fire. fire safety components: the specific building elements, structures and procedures, which the architect can use tactically to achieve fire safety (e.g. they may include fire doors, sprinklers, escape stairs, and fire drills). fire safety objectives: the objectives which the architect must satisfy in order to achieve a fire-safe building, normally life safety and property protection. fire safety tactics: the tactics which the architect can adopt in order to satisfy the fire safety objectives, normally prevention, communications, escape, containment and extinguishment. fire stop: a seal provided to close an imperfection of fit or design tolerance between elements or components, to restrict the passage of fire and smoke. flame: zone of combustion in the gaseous phase usually with the emission of light. flammable limits: the range of concentrations of flammable vapours to air within which a flame will be produced in the presence of an ignition source. flashover: the transition to a state of total surface involvement in a fire of combustible materials within an enclosure. flash point: the minimum temperature to which a material or product must be heated for the vapours emitted to ignite momentarily in the presence of a flame under specified test conditions.

178

Glossary of Fire Terms

fuel limitation: the control of the amount of fuel within a building or room. fuel load: the amount of potential fuel within a building or room, this includes both the building’s fabric and contents. ignitability: measure of the ease with which a material can be ignited, under specified conditions. ignition: initiation of combustion. ignition prevention: measures taken to reduce the probability of ignition. ignition risk: the probability of ignition. ignition source: a source of energy which initiates combustion. ionisation detector: a smoke detector which can identify the reduction in electrical current across an air gap in the presence of a small radioactive source, when smoke particles are present. insulation: the resistance offered by a material to the transfer of heat. integrity: the ability of a separating element when exposed to fire on one side, to prevent the passage of flames and hot gases or the occurrence of flames on the unexposed side, for a stated period of time in a standard fire resistance test. intumescents: materials which react to heat by expanding and forming an insulating layer. laminated glass: glass which incorporates layers of transparent and translucent intumescent material. loadbearing capacity: the dimensional stability of a material. manual call point: an alarm switch which can be activated by the occupants. neutral plane: the level within a building where the internal air pressure is equivalent to atmospheric pressure. occupancy load factor: a measure for calculating the likely number of people in particular building types for a given floor area. optical detector: a smoke detector which can identify the reduction in light received from a light source by a photo-electric cell when smoke particles are present. passive containment: measures to contain the spread of fire which are always present and do not require the operation of any form of mechanical device (e.g. the fire protection provided to the building structure or the fire resisting walls provided to divide a building into different compartments). phased evacuation: the planned evacuation of a building in stages. place of safety: an area to which the occupants can move, where they are in no danger from fire. pre-action sprinkler systems: one which is “dry”, but where water is allowed in on a signal from a more responsive detector (usually smoke) in advance of the heads being triggered. pre-mixed flames: flames from combustion where the fuel is a gas and is already mixed with oxygen. pressurisation: the technique whereby staircases or corridors are pressurised so that they can resist the inflow of smoke. prevention: the fire safety tactic of ensuring that fires do not start by controlling ignition and limiting fuel sources.

179

Glossary of Fire Terms

progressive horizontal evacuation: evacuation of the occupants away from a fire into a fire-free compartment or sub-compartment on the same level. protected shaft: a shaft which enables persons, air or objects to pass from one compartment to another, and which is closed with fire-resisting construction. radiation: the transfer of heat without an intervening medium between the source and the receivers. re-cycling (or re-setting) sprinkler system: a sprinkler system where the heads can be closed once the fire is extinguished so that water damage is minimised. refuge: a place of safety within a building. re-setting (or re-cycling) sprinkler system: a sprinkler system where the heads can be closed once the fire is extinguished so that water damage is minimised. rising mains: vertical pipes installed within tall buildings (usually over 18 m), which have a fire service connection or booster pump at the lower end and outlets at different levels within the building. sacrificial timber: the technique of deliberately over sizing timber elements to enhance their fire resistance. smoke: visible part of the fire effluent. smoke curtains: barriers which can restrict the movement of smoke. smoke layering (or smoke stratification): the process whereby different layers or zones develop within smoke due to the buoyancy of the gases involved. smoke load: the amount of potential fuel within a building or room which will produce smoke. smoke obscuration: reduction in visibility due to smoke. smoke reservoirs: areas in the ceiling of a space in which smoke will collect. smoke stratification (or smoke layering): the process whereby different layers or zones develop within smoke due to the buoyancy of the gases involved. smoke venting: the technique of allowing smoke to escape from a building, or of forcing it out by mechanical means. soot: fine particles, mainly carbon, produced and deposited during the incomplete combustion of organic materials. spontaneous ignition temperature: the minimum temperature at which ignition is obtained under specified test conditions without any source of pilot ignition. sprinklers: auto-suppression systems using water sprays to extinguish small fires, and contain growing fires until the fire services arrive. stage 1 escape: escape form the room or area of origin. stage 2 escape: escape from the compartment or sub-compartment of origin by the circulation route to a final exit, a protected stair, or an adjoining compartment offering refuge. stage 3 escape: escape from the floor of origin to ground level. stage 4 escape: final escape at ground level. structural elements: loadbearing elements of the building, in particular floors and their supporting structures (e.g. columns, loadbearing walls). structural protection: fire resistance provided to structural elements.

180

Glossary of Fire Terms

sub-compartments: fire and smoke tight areas into which a building can be divided to reduce travel distances, offering 30 minutes of resistance. sub-compartment wall: a fire-resisting wall used to separate one sub-compartment from another and having a minimum period of resistance of 30 minutes. surface spread of flame: the propagation of flame away from the source of ignition across the surface of a liquid or solid. toughened glass: glass which has been toughened to achieve higher levels of stability and integrity. trade-offs: the technique of providing equivalent levels of fire safety through different fire safety measures. traditional fire safety design: design which considers the building as series of components and attempts to achieve fire safety by ensuring all such components meet a specified performance standard. travel distance: the distance to be travelled from any point in a building to a place of safety, often specified in terms of the different stages of escape. triangle of fire: a description of the three ingredients necessary for a fire (heat, fuel and oxygen). unprotected areas: unprotected areas in relation to a side or external wall of a building means: (a) a window, door or other opening, (b) any part of the external wall which has a fire resistance less than 60 minutes, or 30 minutes if single storey (integrity and load bearing capacity only), and which provides less than 15 minutes fire resistance (insulation). wet rising main: a rising main normally kept permanently charged with water. wet sprinkler system: a sprinkler system where the pipework is kept permanently charged with water.

181

Index

Page numbers printed in bold type refer to figures; those in italic to tables. References to entries in the glossary of terms are indicated by an asterisk (*) Acceptability, of safety levels 13–15, 176* Access for fire services 94, 95, 109, 111 Access rooms 55, 55 Active containment 63, 77–9, 176* pressurization 79–81, 179* smoke venting 81–7, 180* see also Passive containment Acts of Parliament 107 see also Legislation, and specific Acts of Parliament Addressable systems, of fire detection 36–8, 37, 176* Adjoining buildings 63, 77 Advisory services 136–7 Air conditioning, and smoke venting 86 Aircraft/airport fires 61, 91 Air entrainment 8 Airlocks 79 Airport terminals, fire modelling 50 Alarm systems see Fire alarm; Fire-alarm systems Alternating sprinkler systems 91, 176* American Society for Testing and Materials (ASTM) see ASTM standards American Society of Civil Engineers 143 American Society of Mechanical Engineers (ASME) 143 Appraisal see Assessment Approved Documents/Guides 107, 110, 110–11 Arson see Fire-raising Assembly buildings alarms 42 compartment size 76 escape lighting 61

182

fires in 55 licensing 120 occupancy characteristics 48, 52 signs 41 structural fire resistance 66 travel distances 57 see also Entertainment premises; Sports grounds Assessment 96–105, 176* fire precautions 98, 99–100, 102 fire risks 16–17, 98, 99, 101–2, 122 methodology 97–8 three-part approach 97–8, 98 Assessors 103–5 Association for Specialist Fire Protection 137 ASTM standards 143, 145, 146 Audit 29, 97, 103, 176* Auto-suppression 90–3, 176* carbon dioxide 92 cost 92 deluge systems 92 drenchers 92 dry powder 92 equivalency 93 foam 92 water spray systems 92 see also Sprinklers Backdraught 5 Benchmarks 100, 103 Bradford City football stadium 13, 46, 49 BRE 129–31, 136 Break glass (manual) call points 31, 179* Brick, fire resistance 6, 71

Index

Bridgeheads 93, 93, 176* British Standards (BS) 121–8 see also under specific subject headings British Standards Institution (BSI) 121 Building Act 1984 108 Building Construction and Safety Code (US) 141 Building contents 28–9 Building fabric 25–7 Building layout 21–2, 31 Building materials 6, 25–7 certification 25, 146 characteristics 25–6 coatings 127 fire resistance 22, 26, 65, 68–72, 125, 146 fire tests 65, 143, 146 Building regulations administration of 110 Approved Documents 110, 110–11 China 167–8 England and Wales 108–13 Hong Kong 159–65 Northern Ireland 116–18 performance-based 107–8, 113–15, 153–6, 163–4, 168–70 Scotland 113–16 United States 138–44, 150–3 Building Research Establishment (BRE) see BRE Building (Scotland) Act 1959 113–16 Building (Scotland) Regulations 2004 113 Building services 22 BS 8313: Accommodation of building services in ducts 127 openings for 72 Building structure see Structural elements Building type compartment size 76 fuel loads 66 occupancy characteristics 52, 52–3 occupancy estimation 48 structural fire resistance 66 travel distance 57 see also specific building types Burning brands 77, 78, 176* Bus garages 34–5 Bush fires 46 Cables, openings for 72 Cairo Sheraton hotel 38 Call points, manual (break glass) 31, 179* Carbon dioxide (CO2) 8 in auto-suppression 92

BS 5306: Code of practice for fire extinguishing installations and equipment on premises 126 as extinguishing agent 88, 88–9 Carbon monoxide 7–8, 8 Care homes see Residential care premises Carelessness 20–1, 22 Car parks, open-sided compartment size 76 occupancy characteristics 48, 52 structural fire resistance 66 travel distances 57 Cathedrals fire detectors 34, 35 fires in 19, 20 Ceilings, interior finishes 27 Certification BRE Certification 129 building products 25, 146 CERTIFIRE 137 fire certificates 112 of fire risk assessors 104 Chairs, stacking 28 Charring, of wood 69, 69 China 165–71 Chip-pans 21 Circulation routes/areas 31, 45 BS 5395: Stairs, lobbies and walkways 126 Cladding materials 77 BS 8414: Fire performance of external cladding systems 124 Coatings BS 8202: Coatings for fire protection of building elements 127 see also Intumescents Collapse, of buildings 67, 67 Combustibility 25, 176* Combustion 1–2, 176* Combustion products 6 Communication 12, 30–44, 176* Communication systems requirements of 30 see also Detection; Fire alarm; Firealarm systems; Fire notices; Signs Compartmentation 10, 55, 63, 72–6, 73, 176* and travel (escape) distance 55–8, 74, 75 Compartment fires 3–5, 4, 6, 7 size of enclosure 7 Compartment floors 74, 177* Compartments 176* more than one storey 74 numbers of 72, 74

183

Index

Compartments (cont.): protection time 55 size 72–3, 74–5, 75, 76 subcompartments 55, 58, 59, 74, 75, 181* Compartment walls 177* doors/ducts through 72 subcompartment walls 181* Competence, of assessors 104 Computers BS 6266: Fire protection for electronic equipment installations 127 microprocessors, in fire-alarm systems 36 smoke modelling 35, 50 Concrete fire resistance 70–1 heat resistance 6 spalling 71 Conduction 3, 177* Construction (Design and Management) (CDM) Regulations 2007 119 Consultancy services 136–7 Containment 12, 62–87, 177* see also Active containment; Passive containment Convection 3, 4, 177* Conventional systems, of fire detection 36, 36, 177* Cooking appliances 19, 20–1 Cooling (decay) period 5, 5 Crime concealment 23 Crowd management, in escape 49 Decay (cooling) period 5, 5 Deluge systems 92 Department of Education, fire safety guidance 132–3 Department of Health, fire safety guidance 132 Detection 30–5 automatic, while building unoccupied 31 BS 5839: Fire detection and alarm systems for buildings 126–7 flame detectors 34 heat detectors 33–4 ionization detectors 32, 179* light detectors 34 manual detection 31 optical detectors 32, 35, 179* optical duct sensors 35 point detectors 34

184

smart detectors 37 smoke detectors 32–3, 35, 46–7 smoke sampling 35 thermal turbulence detectors 34–5 see also Fire-alarm systems Diffusion flames 2, 177* Disabled people escape 49–50 BS 6440: Powered lifting platforms . . . for use by persons with impaired mobility 127 escape route widths 57–8 lifts for 59–60 refuge 58, 59 rescue 45, 60 Discothèques, fires in 46, 48, 61 Distance to boundary 78 Doors BS EN 1155: Electrically powered hold open devices for swing doors 128 in compartment walls 72, 76 escape route widths 57–8 fire resistance 76 inlet air 85 pass or password controlled 50 see also Emergency exit devices; Fire doors Door wedges 72 Drenchers 92 Dry powder 5, 88, 89 in auto-suppression 92 Dry risers 94, 177* Dry sprinkler systems 91, 177* Ducts 72 BS 8313: Accommodation of building services in ducts 127 optical duct sensors 35 Dwellings BS 5446: Specification for Components of Automatic Fire Alarm Systems for Residential Premises 126 fires during night 38–9 fires in 2, 3 ignition sources 19, 19 injury statistics 9, 9 lower standards of fire safety 14 in multiple occupation 120 occupancy characteristics 48, 52 as separate compartment 75 smoke detectors 46–7 sprinklers 92 structural fire resistance 66 travel distance 57

Index

Earthquakes 20 Educational buildings 132–3 Egress 45, 177* v. refuge 59 Electrical cables, openings for 72 Electrical fires 88, 88, 90, 92 Electrical installation 22 Electronic equipment, BS 6266: Fire protection for electronic equipment installations 127 Emergency exit devices BS EN 1125: Panic exit devices operated by a horizontal bar 128 BS EN 179: Emergency exit devices operated by a lever handle or push pad for use on escape routes 127 Emergency lighting 61, 177* BS EN 1838 (BS 5266): Emergency lighting 126, 128 see also Escape lighting Empire Palace theatre, Edinburgh 55 Enactments 107 Enclosed spaces see Compartment fires Entertainment premises Discothèques 46, 48, 61 Empire Palace, Edinburgh 55 Summerland Leisure Centre, Isle of Man 24, 26–7, 51 see also Assembly buildings; Sports grounds Envelope protection 64, 77, 177* Equivalency 14–15, 110, 177* of auto-suppression 93 Escape 12, 45–61 basic strategies 45 Building Regulations 108, 110 crowd management 48 escape times 55 escape (travel) distance 53, 56–8, 57, 74, 75, 181* speed of 50 stage 1 (out of room of origin) 53–4, 180* stage 2 (out of compartment of origin) 55–8, 180* stage 3 (out of the floor of origin) 58–60, 180* stage 4 (final escape at ground level) 60, 180* stages of 53 from windows 60–1 see also Evacuation Escape lighting 61, 177* Escape stairs 59 European Federation of Fire Separating Element Producers 137

European Standards 122, 125–6, 127–8 Evacuation phased 53 progressive horizontal evacuation 58, 59, 62 strategy 39, 45 vertical 60 see also Escape Exits final exit 60, 177* minimum numbers of 59 minimum widths 57–8 signs 41, 41 see also Emergency exit devices External fire spread 63, 111 Building Regulations 109 External walls 77 BS 8414: Fire performance of external cladding systems 124 unprotected areas 181* Extinguishers 89, 90 Extinguishing agents 5, 88–9 in auto-suppression systems 91 carbon dioxide (CO2) 88, 88–9 dry powder 5, 88, 89 foam 88, 88 halogenated hydrocarbons (halons) 89 water 5, 88, 88 Extinguishment 12, 88–95, 177* Fabrics 28 BS 5438: Methods of test for flammability of fabrics 124 Factory buildings compartment size 76 occupancy characteristics 48, 52 structural fire resistance 66 travel distances 57 Fairfield Old People’s Home, Edwalton 47 Familiarity of occupants with building 50–1 Fast response (residential) sprinklers 92 Fatalities, causes 7–8 see also Fire statistics Fa Yuen Street, Hong Kong 163 Final exit 60, 177* Financial gain, fires started for 23 Fire 177* Fire alarm 38–41 Building Regulations 108, 110 coded messages 39 for fire services 40 for occupants 38–40 185

Index

Fire alarm (cont.): pre-recorded messages 40 public announcements 39 for staff 39 strategy 39 types of 38 visual signal 38 Fire-alarm systems actuating other systems 40 addressable systems 36–8, 37, 176* BS 5446: Specification for components of automatic fire alarm systems for residential premises 126 BS 5839: Fire detection and alarm systems in buildings 126–7 BS 5979: Remote centres for alarm systems 127 BS EN 54–11: Fire detection and alarm systems – manual call points 127 Commissioning 38 conventional systems 35–6, 36, 177* fire-alarm panels 36, 40 manual (break glass) call points 31, 179* microprocessors in 36, 37 purpose, life safety/property protection 30 see also Detection; Fire alarm Fire assessors 103–5 Fire blankets 90 Fire brigade services see Fire services Fire Certificates 25, 112 FIRECODE guidance documents 132 Fire codes China 167–8 healthcare premises 132 Hong Kong 159–65 performance-based 153–4 United States 139, 141 Fire detection see Detection Fire doors 76, 177* BS 7273: Code of practice for the operation of fire protection measures 127 BS 8214: Fire door assemblies 127 Fire engineering 178* Fire engineering approach 16–17 BS 7974: Application of fire safety engineering principles to the design of buildings 121–2 China 169–70 Hong Kong 162–4 United States 154

186

see also Performance-based standards Fire extinguishment see Extinguishment Firefighting equipment auto-suppression systems 90–3, 176* BS 5306: Fire extinguishing installations and equipment on premises 126 BS 9990: Non-automatic firefighting systems in buildings 127 hand-held 90 hose reels 90 manual 89–90 signs 42 see also Fire hydrants; Fire services; Sprinklers Firefighting lifts 93 Fire growth 3–6 see also Fire spread Fire growth curve 4, 5, 178* Fire hazards 98, 99, 178* warning signs 42, 43 Fire hydrants BS 3251: 1976 Indicator plates for hydrants and emergency water supplies 126 BS 5041: Fire hydrant systems equipment 126 Fire Industry Association 136 Fire load 25, 178* see also Fuel load Fire modelling 47, 50 FireNet 137 Fire notices 42–3, 44 see also Signs Fire point 2, 178* Fire precautions 178* assessment 98, 99–100, 102 balancing risks 98, 100, 103 BS 9999: Code of practice for fire safety in the design, management and use of buildings 122 design issues 100 management issues 100 Fire Precautions (Places of Work) Regulations 112 Fire prevention see Prevention Fire propagation 26, 178* Fire protection 178* BS 8202: Coatings for fire protection of building elements 127 structural 63, 64–72, 180* Fire Protection Association (FPA) 131, 136

Index

Fire-raising, deliberate 23–5 Fire resistance 26, 68–72, 178* brick 71 and building type 66 concrete 70–1 definition 67–8 doors 76 glass 71–2 maintaining 22 methods of improving 69 standards 65, 146 steel 69–70 wood 69, 69 Fire risk 178* assessment 16–17, 99, 101–2, 122 assessors 103–4 balanced by fire precautions 98, 100–1, 103 design issues 99 hidden problems 164–5 management issues 99 minimization 9–10 Fire Risk Assessment Competency Council 104 Fire safety components 10, 12–13, 178* Fire safety design 9–17 acceptability 13–14 BS 9999: Fire safety in the design, management and use of buildings 122 communication 12, 30–44, 177* equivalency 14–15, 93, 177* fire engineering approach 16–17, 121–2, 154, 162–4, 169–70 firefighting operations, safety of 11 risk minimization 10 safety principles 10 trade-off 14 traditional 15–16, 181* see also Containment; Escape; Extinguishment; Prevention Fire safety management 29 Fire safety objectives 10, 10–11, 11, 178* Fire Safety Order 111–13 Fire Safety (Scotland) Regulations 2006 116 Fire safety strategy 29 Fire safety tactics 10, 11–12, 13, 178* Fire safety training 29, 31, 52 Fire science 1–9 Fire (Scotland) Act 2005 116 Fire separation 21–2, 31 see also Compartmentation

Fire services access for 94–5, 95, 109, 111 bridgeheads 93, 93, 177* calls to 40 facilities 94, 109, 111 rescue 60 rising mains 94, 180* Fire severity 6, 19 Fire size 84 Fire spread 6, 6, 77 to adjoining properties 63, 77 Building Regulations 109, 110–11 speed of 46 surface spread of flame 26, 77, 181* Fire statistics 2, 3 fatalities/injuries 2, 3, 9, 9 fire spread 6, 6 ignition sources 9, 9, 19 by location 2, 3 Fire stops 72, 178* Fire tests 65 BS 476: Fire tests on building material and structures 122–4 BS 6336: Guide to development and presentation of fire tests and their use in hazard assessment 127 European standards 125–6 United States 143, 146 see also Certification Flame 2, 178* Flame detectors 34 Flame flicker 34, 35 Flame retardancy 22, 27, 28, 69 Flammable limits 2, 178* Flashover 4, 5, 178* Flash point 2, 178* Floor coverings, BS 4790: Method of determination of the effects of a small ignition source on textile floor coverings 124 FMGlobal 143, 146 Foam in auto-suppression 92 combustion-modified 28 as extinguishing agent 88, 88 polyurethane 9, 28 Forest fires 20 Fuel, arrangement of 7 Fuel limitation 25–9, 179* building contents 28–9 building fabric 25–7 Fuel load 7, 66, 179* and fire resistance 65

187

Index

Furnishings 28 British Standards (BS) 124 BS 5438: Methods of test for flammability of fabrics 124 Furniture BS 5852: Methods of test for assessment of the ignitability of upholstered seating 124 BS 7177: Specification for resistance to ignition of mattresses, divans and bed bases 124 Garley Building, Hong Kong 161 Georgian-wired glass 71 Glass fire resistance 71–2 Georgian-wired 71 laminated 71, 179* toughened 71, 181* Glass and Glazing Federation 137 Glossary of terms, BS 4422: Fire – vocabulary 126 Green buildings 163 Halogenated hydrocarbons (halons) 89 Hazards see Fire hazards Health and Safety at Work Act 1974 119 Healthcare premises 132 see also Hospitals Health Technical Memoranda (HTMs) 132 Heat 6–7 dissipation 68, 69, 70, 70 fire spread to adjoining properties 77, 78 heat transfer 3, 3, 4 threats from 62, 63 Heat detectors 33–4 ‘rate of rise’ detectors 33 High-rise buildings evacuation 53 fire containment 62 fire-fighting equipment 161 fire service facilities 93–4 fires in 40, 53 Hillsborough football ground, Sheffield 49 Hong Kong 159–65, 170–1 Hose reels 90 BS 5306: Fire extinguishing installations and equipment on premises 126 Hospitals compartment size 76 escape lifts 59–60 fire alarm 39

188

FIRECODE guidance documents 132 Health Technical Memoranda (HTMs) 132 occupancy characteristics 48, 52 and refuge 58, 62 secure units, escape v. security 50 structural fire resistance 66 travel distance 57 Hotels, fires in 38, 40, 47 Houses in Multiple Occupation (HMOs) 120 Human carelessness 20–1, 22 Hydrogen chloride 8 Hydrogen cyanide 8 Ignitability 25, 26, 179* Ignition 1–2, 179* classification of sources 18 deliberate fire-raising 23–5 human carelessness 20–1, 22 natural phenomena 19–20 technological failures 21–2 Ignition prevention 18–25, 179* Ignition risk 19, 179* Ignition sources 9, 9, 19, 179* dwellings 19, 19 non-dwellings 19, 19, 21 Infra-red detectors 34, 35 Injuries, causes 9, 9 Inlet air 85, 86 Inner rooms 54, 55 Institution of Fire Engineers (IFE) 136 Insulation 68, 68, 179* for steel 70, 70 Insurance property protection priority 16 repair v. rebuilding 64 Insurance frauds 23 Integrity 68, 68, 179* Interior finishes 27 International Building Code (US) 141, 144, 146 International Code Council (US) 147–9 Performance Code for Buildings and Facilities 154–6, 155 International Fire Code (US) 142, 146 International Organization for Standardization (ISO) 121, 125 Interoperability standards 145 Intumescent Fire Seals Association 137 Intumescents 70, 179* BS 8202: Coatings for fire protection of building elements 127 in glass 71 Ionization detectors 32, 179*

Index

King’s Cross, London 27 Laminated glass 71, 179* Layering (stratification), of smoke 81–2, 180* Legislation 106–21 as disaster response 13–14 existing buildings 108 local 120 new buildings 108 Northern Ireland 116–18, 119 Scotland 113–16 specific building types and activities 120–1 see also specific Acts of Parliament Licensing 120 Life safety sprinklers 92 Life safety v. property protection 11, 16, 30 Lifting platforms, BS 6440: Powered lifting . . . for use by persons with impaired mobility 127 Lifts 59–60 BS EN 81: Safety rules for the construction and installation of lifts 127 protected 93 Light 6 Light detectors 34 Lighting emergency lighting 61, 126, 128, 177* escape lighting 61, 177* Lightning 19, 20 Lightning-conductor systems 20 bell-tent protection 20 Lines of defence 23, 24 Linings (internal) 27 Loadbearing capacity 68, 68, 179* Lobbies BS 5395: Stairs, lobbies and walkways 126 two-door protection 79 Maintenance manuals 22, 29 Manchester Airport fire 61 Manual (break glass) call points 31, 179* Materials see Building materials MGM hotel, Las Vegas 40 Microprocessors, in fire-alarm systems 36, 37 Mobility, of occupants 49–50, 58 see also Disabled people escape

National Council of Examiners for Engineering and Surveying 143 National Fire Protection Association (NFPA) 142, 149–50 Building Construction and Safety Code 154, 156 Natural phenomena, causing ignition 19–20 Neutral plane 85–6, 87, 179* New York, World Trade Building 53 Nitrogen oxides 8 Noisy environments, fire alarm 38, 42 Non-dwellings, fires in 2, 3 ignition sources 19, 19, 21 injury statistics 9, 9 Northern Ireland, legislation 116–18, 119 Occupancy characteristics 45–6 and building type 52–3 Occupancy load factor 48, 48, 179* Occupants escape strategy 45–6 familiarity with building 50–1 and fire alarm 38–40 mobility 49–50 numbers of 47–8 response to fire 51–2 sleeping risk 46–7 Office buildings compartment size 76 occupancy characteristics 48, 52 structural fire resistance 66 travel distances 57 Openings, fire stopping 72 Optical detectors 32, 35, 179* Optical duct sensors 35 Oroglass 26–7 Oversizing of timber 68 Oxygen 1–2, 5, 7 Paint, photoluminescent 61 Passive containment 64–72 compartmentation 10, 55, 63, 72–6, 176* envelope protection 64, 77, 177* protection of structural elements 64–7 structural protection 63, 64, 64–72 see also Active containment; Fire resistance Passive surveillance 24, 31 Performance-based standards 107–8, 113–15 China 168–70

189

Index

Performance-based standards (cont.): Hong Kong 163–4 United States 153–6 see also Fire engineering approach Phased evacuation 39, 53 Photoluminescent paint 61 Pipework, openings for 72 Place of safety 1155 Plastics 27 Point detectors 34 Polypropylene 28 Polyurethane foam 9, 28 Powder see Dry powder Pre-action sprinkler systems 91, 179* Precautions see Fire precautions Pre-mixed flames 2, 179* Pressurization 79–81, 82, 179* Prevention 12, 166, 179* fuel limitation 25–9, 179* ignition prevention 18–25, 179* separating ignition risks from life risks 21–2, 29 spread to adjoining properties 63, 77 Prisons, escape v. security 50 Proban 28 Product certification 25, 146 Progressive horizontal evacuation 58, 59, 62, 180* Property protection v. life safety 11, 16, 21 Protected lifts 93 Protected routes 74 Protected shafts 74, 180* Protection see Fire protection Public address systems, fire alarm 39 Public assembly buildings see Assembly buildings Pyran 71 Pyrobel 71 Pyrostop 71 Pyroswiss 71 Pyrovatex 28 Radiation 3, 4, 77, 78 Re-cycling (re-setting) sprinkler systems 91, 180* Reel hoses see Hose reels Refuge 45, 58, 59, 62, 180* hospital design 62 v. egress 59 Regulations 107 see also Building regulations; Fire codes Regulatory Reform Act 2001 111

190

Regulatory Reform (Fire Safety) Order 2005 111 Reinforced concrete 70–1 Rescue 45, 60–1 Residential buildings BS 5446: Specification for Components of Automatic Fire Alarm Systems for Residential Premises 126 BS 9251: Sprinkler systems for residential and domestic occupancies 127 compartment size 76 occupancy characteristics 48, 52 smoke detectors 46–7 structural fire resistance 66 travel distance 57 unfamiliarity with building 51 see also Dwellings Residential care buildings compartment size 76 fire risks 52, 52 fires in 47, 105, 129 occupancy characteristics 48, 52 and refuge 58 structural fire resistance 66 travel distance 57 Response of occupants to fire 51–2 ‘Responsible person’ 104, 112 Retail buildings compartment size 76 escape route lighting 41 fire alarm 40 occupancy characteristics 48, 52 structural fire resistance 66 travel distances 57 Rising mains 94, 180* Risk see Fire risk Roof collapse of 67, 67 as source of burning brands 77, 78 Room fires see Compartment fires Rose and Crown, Saffron Walden 47 Rosepark care home, Uddingston, North Lanarks 47, 105, 129 Rubbish fires 21, 22 Sacrificial timber 69, 180* Schools, fires in 23 see also Educational buildings Scotland, legislation and standards 113–16 Security v. fire safety 50 Severity of fires 19 Shafts, protected 74, 180*

Index

Shopping centres escape route lighting 41 fire alarm 40 see also Retail buildings Signs 41–2 BS 5499: Fire safety signs, notices and graphic symbols 126 fire notices 42–3, 44 Six-Nine Discothèque, La Louvière 61 Skip fires 21, 22 Sleeping risk 46–7 Smart detectors 37 Smoke 7–9, 180* appearance 8 constituents 8 deaths from 7–8 density 8 smoke logging 13 stratification/layering 81–2, 180* threats from 62, 63 toxicity 8–9 visibility in 8, 26 Smoke control 78–87 BS EN 12101: Smoke and heat control systems 128 pressurization 79–81, 82, 179* smoke venting 81–7, 83, 180* Smoke curtains 82, 84, 180* Smoke detectors 32–3, 34, 35 dwellings and residential premises 46–7 Smoke load 7, 26, 180* Smoke locks 79 Smoke modelling 35, 47, 50 Smoke obscuration 26, 180* Smoke reservoirs 82–5, 83, 180* Smokers’ materials 20, 21 Smoke sampling 35 Smoke venting 81–7, 83, 180* Smoking areas 21 Smouldering 5 Sodium bicarbonate 89 Soot 180* Spontaneous ignition temperature 2, 180* Sports grounds Bradford City football stadium 13, 46, 49 Hillsborough football ground, Sheffield 49 Sprinklers alternating systems 91, 176* BS 9251: Sprinkler systems for residential and domestic occupancies 127

and compartment size 75–6 dry systems 91, 177* fast-response (residential) 92 and fire size 84 installation standard 145 mounting of heads 91 pre-action systems 91, 179* re-cycling (re-setting) systems 91, 180* and smoke venting 86–7, 91 v. smoke control 78 water suppliers 92 wet systems 91–2, 180* Stability 67, 68, 68 Stable phase 5 Stacking chairs 28 Staff training see Training Staircases pressurization 80, 179* width 59 Stairs, BS 5395: Stairs, lobbies and walkways 126 Standards British Standards (BS) 121–8 China 168 United States 142–3, 144–7, 149–50 see also Benchmarks Stardust Disco, Dublin 46, 48 Statutory Instruments 107 Steel fire resistance 69–70 heat dissipation 70, 70 heat effect on 6 insulation for 70, 70 in reinforced concrete 70–1 Steel Construction Institute (SCI), publications 134 Storage buildings 28 compartment size 76 occupancy characteristics 48, 52 sprinkler systems 91 structural fire resistance 66 travel distance 57 Storage space 21, 28 Strategy evacuation 45 fire safety 29 fire warning and alarm 39 Stratification (layering), of smoke 81–2, 180* Structural elements 26–7, 180* collapse of roof/upper storeys 67, 67 protection 63, 64–7

191

Index

Structural fire resistance 66 Structural protection 63, 64–72, 67, 180* Subcompartments 58, 59, 75, 181* protection time 55 walls 74, 181* Summerland Leisure Centre, Isle of Man 24, 26–7, 51 Surface spread of flame 26, 77, 181* Surveillance, passive 24, 31 Sustainable buildings 163 Tall buildings see High-rise buildings Taunton sleeper fire 52 Technological failure, causing ignition 21–2 Television, closed-circuit 24 Terrorist attack 24–5 Textbooks 134–6 Theatres see Entertainment premises Thermal turbulence detectors 34–5 Timber 6 BS 5268: Structural use of timber 126 sacrificial timber 69, 180* test certificates 133 see also Wood Timber Research and Development Association (TRADA), publications 133–4 Toughened glass 71, 181* Toxic gases 8–9 Trade associations 136–7 Trade-offs 14, 98, 181* Train fires 52 Training fire safety training 29, 31, 52 hand-held equipment 90 Travel (escape) distance 53, 181* and compartmentation 56, 56–8, 74, 75 Triangle of fire 2, 18, 88, 181* Ultra-violet detectors 34 Underwriters Laboratories Inc (UL) 143, 146 United States 138–57 building codes 138–44, 150–3 fire codes 142–4 product certification 146

192

registration and licensing of architects and engineers 143 standards 142–3, 144–7, 149–50 Unprotected areas 77, 181* Upstands 85 Vandalism, malicious/casual 23 Ventilation and fire growth 4, 5–6, 7 mechanical v. natural 85, 86 and pressurization 79, 80, 81 smoke venting 81–7, 83 Ventilation-controlled fires 7 Ventilation systems 40–1 Venting see Smoke venting Visibility, in smoke 8, 26 Walls external 77 interior finishes 27 unprotected areas 77 see also Compartment walls Warehouses see Storage buildings Warrington certification 137 Water as extinguishing agent 5, 88, 88 hose reels 90 Water spray systems 92 Water supplies BS 3251: 1976 Indicator plates for hydrants and emergency water supplies 126 sprinklers 92 Wet risers 93, 181* Wet sprinkler systems 91–2, 181* Windows fire resistance 71–2 fire spread 77 in rescue opportunities 60–1 size and shape 7 Wood 68–9, 69 see also Timber Wood Information Sheets (WIS) 133 see also Timber Woolworth’s, Manchester 9, 28, 60 Workplaces, Fire Precautions (Places of Work) Regulations 112 World Trade Building, New York 53 York Minster 19

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