Introduction to Fire Safety Management

Figure 7.1
Triangle of fi re
FUEL
Flammable gases
Flammable liquids
Flammable solids 
OXYGEN
Always present in the air
Additional sources from
oxidising substances 
IGNITION SOURCE
Hot surfaces
Electrical equipment
Static electricity
Smoking/naked flames
Decay
Fully developed
Growth
Induction
Time
(a)
Rate of heat release
Figure 7.3
Stages of combustion or fi 
re growth 
(a)
fl ashover zone
Decay
Fully developed
Growth
Induction
Time
(a)
Rate of heat release
7.2.2 Stages of combustion
There are four generally acknowledged stages con-
tained within the process. These start at the 
induction
stage where the component parts of the triangle come 
together and initiate the reactions.
The 
growth
stage, where supplied with an uninter-
rupted level of oxygen or fuel the reactions become 
rapid and grow in intensity, creating large volumes of 
smoke (unburnt products of pyrolysis) the time taken 
in the growth of a fi re may be from a few minutes to 
several hours dependent upon the prevailing conditions. 
The point at which the fi re involves all the combust-
ible materials within the room or area is known as the 
Figure 7.2
Diagrammatic representation of the fi 
re 
process
Fuel
Oxygen
Ignition/heat
Fire
Smoke
Heat

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118
and its location, e.g. whether it is from the building 
components itself (refer to Chapter 9 on building design 
and construction) or materials introduced to the building 
such as plastics, furnishings, etc. As with any chemical 
reaction, the control of the amounts and levels of the 
component parts (heat, fuel and oxygen) has a signifi -
cant bearing on the rate of reaction and the heat output. 
Thus should a fi re involve materials such as polystyrene, 
audio/video tape or other known high heat releasing 
materials then the speed at which the fi re develops will 
increase.
The same will be the case if chemicals such as 
oxidising agents are involved. When heated, oxidis-
ing agents give off large amounts of oxygen which can 
rapidly increase both the growth and the spread of 
fi re. The control of air (oxygen) in ventilation systems 
and ducts also has an impact upon fi re growth and fi re 
spread.
It is appropriate also to consider the effects of a