Introduction to Fire Safety Management

smouldering
fi re which only occur in porous mater ials 
such as paper, cardboard, sawdust, fi breboard, etc. 
(carbonaceous).
Smouldering is the combustion of a solid in air which 
does not produce a fl ame. The smouldering process is 
very slow and can go undiscovered for a very long time; 
it can, however, produce a large amount of smoke. The 
smoke must accumulate and reach its lower fl ammability 
limit before ignition can occur. Given favourable conditions 
smouldering will undergo a transition to fl aming, such as 
in the case of a cigarette igniting upholstered furniture. 
Due to the fact that the mechanism is not fully understood 
prediction as to when the smouldering to fl aming transi-
tion occurs is diffi cult. Following a fi re it is also pos-
sible that small conglomerations of material can be left 
smouldering (bull’s eyes) which if supplied with suffi cient 
oxygen can cause reignition.
Some chemical reactions also have the ability to 
extract heat from surrounding materials; these are called 
endothermic
reactions, one such reaction can be seen 
when liquid carbon dioxide (CO
2
) is used when tackling a 
fi re using a portable fi re extinguisher. The energy required 
to change the liquid CO
2
into a gas (known as the latent 
heat of vaporisation) is taken from the surrounding 
material resulting in the formation of ice on the body of 
the extinguisher.
7.2.3 Fire 
initiators
In order for a fi re to start there has to be suffi cient heat 
from an initiator or ignition source. Sources of ignition 
can be found in every workplace and home.
These sources of ignition could be open fl ames, hot 
surfaces, electrical sparks (internal or external), electrically 
generated arcs, friction (machinery), chemical reactions, 
or even the compression of gases. This is not an exhaus-
tive list, the causes and prevention of fi res are discussed 
in the following chapter leaving this chapter to look at the 
principles of fi re and explosion.
Previously the Offi ce of the Deputy Prime Minister 
(ODPM) produced statistics in relation to the types, 
numbers, etc. of fi re and fi re deaths/injuries.
From the statistics it is possible to identify the 
sources of ignition and the number of occasions that 
these ‘initiators’ have been considered to start a fi re:
➤
Smokers’ 
materials
➤
Cigarette 
lighters
➤
Matches
➤
Cooking 
appliances
➤
Space heating appliances
➤
Central and water heating devices
➤
Blowlamps, welding and cutting equipment
➤
Electrical 
distribution
➤
Other electrical appliances
➤
Candles
➤
Other/unspecifi ed.
In addition to those sources identifi ed above other com-
mon sources of heat in the workplace include:
➤
Electrostatic 
discharges
➤
Ovens, kilns, furnaces, incinerators or open hearths
Figure 7.4
Heat, fuel and oxygen combine to initiate a 
combustion reaction

---