Introduction to Fire Safety Management

7 Principles
7.1 Introduction
Previous chapters have discussed the overall management
issues that need to be addressed if a coherent
safety management system is to be established
and implemented in an organisation. As this book is
primarily focused upon fi re safety management and
its principles, a key element that must be addressed is
ensuring an underpinning knowledge of the principles
of fi re and explosion; this chapter will concentrate on
these areas.
An understanding of the principles are critical to
identifying how a fi re will start and spread, the former of
which are known as primary fi re hazards, each of which
has the ability to initiate or start a fi re, or exacerbate a
fi re. These elements will be required when completing a
fi re risk assessment.
Explosion and fi re are interlinked in that on many
occasions fi re occurs after an explosion, it is therefore
essential that those involved with fi re safety and risk
management have a basic knowledge of the causes
and properties of explosion, particularly in relation to
processes involving gases and dusts.
This chapter discusses the following key
elements:
➤ Combustion processes
➤ Ignition of solids, liquids and gases
➤ Fire growth and spread
➤ Explosion and explosive combustion.
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of fi re and
explosion
7.2 The chemistry of fi re
In order to appreciate the differences between fi re and
explosion it is necessary to look at the defi nitions:
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 combustion
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.