Enclosure fires

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Foreword The aim of this book is to provide a deeper understanding of how fi re behaves during enclosure fi res. This book has been written primarily with fi refi ghters in mind. Every year around a hundred people die throughout Sweden as a result of fi re, with most dying in house fi res. Fire also causes extensive damage to property, with the insurance sector putting an estimated fi gure of 3.4 billion Swedish kronor (approx. £260 million) on the value of the property destroyed every year. This is why it is important to prevent fi re. If considerable resources are channelled into fi re prevention this can reduce both the number of deaths and the cost. When a fi re breaks out it is vital that it can be tackled at an early stage, taking the appropriate action. The aim of this book is to help provide a deeper understanding of how fi re behaves during enclosure fi res. It focuses on understanding the processes involved in an enclosure fi re. The main purpose, however, is not to look at how to actually fi ght this type of fi re, by using smoke venting or applying a particular extinguishing medium, for instance, even though appropriate actions like these will be discussed in some sections. When discussing fi refi ghting measures, reference will be made instead to relevant manuals dealing with smoke venting and extinguishing media. Nor does this book claim to provide an exhaustive insight into this area. For instance, a fi re’s behaviour in industrial premises is different, compared to in house fi res. This book mainly describes fi res in smaller areas such as fl ats or houses. Firefi ghters need to have basic knowledge about the factors controlling the behaviour of these types of fi re. In this situation, as with other operations, there is a great deal of pressure in terms of taking the right course of action. It is also obviously very important to be familiar with and look out for the warning signs which can be picked up during an operation. During the last 10 years great strides have been made in the research into these areas. This has led to a change in the approach to compartment fi res in certain respects. Some of this research provides the basis for this book, along with the practical experience of the local fi re service. 7
8 The book is intended to provide the basic material for teaching about fi re development in Sweden’s Rescue Services Agency colleges. This is the group which the book is mainly targeted at. It may also be of interest, however, to people in other professions who encounter problems relating to enclosure fi res. I hope that the book will manage to serve this purpose, both in terms of being used as a teacher’s guide and as a basic handbook helping to increase the knowledge about fi re development. I am sincerely grateful for all the assistance I received at the various stages in writing this book. There have been contributions from many people, in fact too many for me to name them individually. But I would like to express my heartfelt thanks to them, one and all. Lars-Göran Bengtsson
Page 1 and 2: Lars-Göran Bengtsson Enclosure fi
Page 3 and 4: The content of this book may not be
Page 5 and 6: 4.4 Risk assessment 99 Smoke gases
Page 10: Overview This book assumes that its
Page 13 and 14: Figure 1. Fire growth curve featuri
Page 15 and 16: Fire extinguished/burnt out Just sm
Page 18 and 19: chapter 2 How a fi re starts People
Page 20 and 21: smoke gases in the compartment, but
Page 22 and 23: Pyrolysis gases material is subject
Page 24 and 25: Ignition time Ignition time can als
Page 26 and 27: Smouldering fi res can therefore re
Page 28 and 29: 2.4.1 Thermal inertia kρc The fl a
Page 30 and 31: grow to 50 cm, then a 1 m high fl a
Page 32 and 33: Flammability in solid materials is
Page 34: 6. The fl ame spread rate varies wi
Page 37 and 38: Figure 22. Smoke gases start to acc
Page 39 and 40: Figure 25. The different sections i
Page 41: The production of unburnt gases is
Page 44 and 45: Heat release rate from a fuel surfa
Page 46 and 47: Carbon monoxide (CO) is the next mo
Page 48 and 49: ment to accelerate, but this is obv
Page 50 and 51: is far too high for a premixed fl a
Page 52 and 53: is fi lled with fuel molecules, con
Page 54 and 55: Figure 33. Flames on the under side
Page 56 and 57: Flammability limits Vent For a prem
Page 58 and 59:
CH4 + 2 + 2 + + 2O2 = CO2 + 2H2O +
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Temperature impact on fl ammability
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energy is required, which can be ex
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ustion takes place in under-ventila
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If turbulence affects the system th
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Neutral plane The differences in pr
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Where the differences in temperatur
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Positive pressure Negative pressure
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Dp = 353(1/Ta - 1/Tg)gh Let us take
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Figure 51 (top). The pressure condi
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Vent just during the early stage of
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In Figure 57 calculations have not
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3.4 Summary In many situations the
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oom and in a fairly closed room (on
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Figure 59. The fi re has spread to
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Figure 60. Flashover occurrence ove
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90 precisely the exact moment when
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The amount of energy released when
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Figure 63. Thermal balance on a fue
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Figure 64. Flame spread under the c
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Access to fuel Figure 67. Fire’s
Page 101 and 102:
The signs indicating that a fl asho
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Figure 69. Different signs indicati
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Smoke gas temperature 700 600 500 4
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106 clear that we need to reach the
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This example illustrates how crucia
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110
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112
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114
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Figure 78. Fire pulsating. Figure 7
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Figure 81 (above). The fi re is abo
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Figure 85. The fi re resumes its de
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122 is suffi ciently big. A fi re
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Figure 89. A backdraught entails a
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Figure 90. The picture shows a vent
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128 The current which results in sm
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130 fans should not be used. You sh
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Figure 97. A larger part is premixe
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Figure 101. There are still combust
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Figure 103. Sauna. A common scenari
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Fires in enclosed spaced with minim
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Figure 107. The smoke gases are str
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Figure 110. The fi xed lance versio
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Four fi re scenarios: 1. The fi re
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146 to occur. If a backdraught occu
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148 Fire at 62 Watts Street The New
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chapter 7 Smoke gas explosion Throu
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ignition source required to ignite
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ity is also affected by turbulence
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7.3.2 Course of action If smoke gas
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Test your knowledge! 1. Why do smok
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Corridor Space in between Sauna app
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164 gases the fl ames would come ou
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Figure 119. Plan drawing of the bas
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168 Glossary Adiabatic fl ame If al
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Heat of combustion, This measures t
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172 Suggested solutions to test que
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174 13. In a closed room there will
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176 6. By cooling down the smoke ga
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Sample calculations Flammability li
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You should bear in mind that this c
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Backdraught Sample calculation: The
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E = (T f/T i)( N b/N u) Tf Ti Nb Nu
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v* = v/(g × h × b) 0.5 , which gi
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188 gram), Institutionen för brand
Page 191 and 192:
Index 62 Watts street 148 Adiabatic
Page 193 and 194:
192 List of fi gures Drawn illustra
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Enclosure fires

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