Introduction to Fire Safety Management

Combustion
– a chemical reaction or series of 
reactions in which heat and light are evolved.
Fire
– chemical reaction brought about by the 
combining of fuel and oxygen and the application of 
suffi cient heat to cause ignition.
Fuel
– can be either a gas, liquid or solid (state). 
The amount of heat required to release a vapour which 
allows combustion to take place will depend upon the 
fuel’s state. For example, a block of wood requires a 
higher level of heat to be applied than petrol.
This is because when heated, combustible mater ials 
give off fl ammable gases or vapours. If the temperature 
is high enough and a suffi cient quantity of oxygen is 
present, ignition of these gases and vapours will occur, 
and a fi re will result, thus as petrol is already producing 
vapours it is easy to ignite.
7.2.1 The 
fi re triangle
The ‘fi re triangle’ is a simple representation of the three 
factors necessary for a fi re to start and once started to 
continue to burn.
All materials have the ability to burn if supplied with 
suffi cient heat to cause the molecules to break down 
and give off vapour.
Once the vapour or gas is released it is that which 
ignites, causing more heat to be released, propagating 
further reactions – the fi re process has begun.
As the material that is involved with the combus-
tion or fi re decomposes the material that is left has less 
ability to react, ultimately causing the fi re to die down 
and go out.
This chapter discusses the following key 
elements:
➤
Combustion 
processes
➤
Ignition of solids, liquids and gases
➤
Fire growth and spread
➤
Explosion and explosive combustion.
7
Principles of fi re and 
explosion

---