Introduction to Fire Safety Management

Introduction to Fire Safety Management
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, oxidising
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
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 transition
occurs is diffi cult. Following a fi re it is also possible
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,
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Figure 7.4 Heat, fuel and oxygen combine to initiate a
combustion reaction
or even the compression of gases. This is not an exhaustive
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 common
sources of heat in the workplace include:
➤ Electrostatic discharges
➤ Ovens, kilns, furnaces, incinerators or open hearths