Introduction to Health and Safety at Work

13.3.1 Fire 
triangle
Fire cannot take place unless three things are present. 
These are shown in Figure 13.2.
The absence of any one of these elements will 
prevent a fi re from starting. Prevention depends on 
Fuel
Flammable gases,
liquids, solids
Ignition source
Hot surfaces
Electrical equipment
Static electricity
Smoking materials
Naked flame
Oxygen
From the air
Oxidizing substances
Figure 13.2
Fire 
triangle.

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Fire hazards and control
205
avoiding these three coming together. Fire extinguish-
ing depends on removing one of the elements from an 
existing fi re, and is particularly diffi cult if an oxidizing 
substance is present.
Once a fi re starts it can spread very quickly from fuel 
to fuel as the heat increases.
13.3.2 Sources of ignition
Workplaces have numerous sources of ignition, some 
of which are obvious but others may be hidden inside 
machinery. Most of the sources may cause an accidental 
fi re from sources inside but, in the case of arson (about 
13% of industrial fi res), the source of ignition may be 
brought from outside the workplace and will be deliber-
ately used. The following are potential sources of ignition 
in the typical workplace:
➤
naked fl ames
– from smoking materials, cook-
ing appliances, heating appliances and process 
equipment
➤
external sparks
– from grinding metals, welding, 
impact tools, electrical switch gear
➤
internal sparking
– from electrical equipment (faulty 
and normal), machinery, lighting
➤
hot surfaces
– from lighting, cooking, heating appli-
ances, process equipment, poorly ventilated equip-
ment, faulty and/or badly lubricated equipment, hot 
bearings and drive belts
➤