FPASA BULLETIN FD 04
PROPERTIES OF FLAMMABLE SUBSTANCES
Solvents, flammable liquids and low melting point solids are used extensively in one form or another in
industry. The presence of quantities of these substances in industrial premises adds significantly to the
fire risk and it is therefore important that users familiarise themselves with the chemical and physical
properties of flammable substances.
This knowledge will assist management in introducing safe storage and handling practices.
The table below lists some of the more commonly used flammable substances and their important
characteristics.
EXPLANATION OF TERMS
Flash point
The flash point represents the lowest temperature at which a substance gives off sufficient flammable
vapour in air to produce a flash on the application of a small flame.
The flash point varies according to whether an open or closed cup test method is employed. A closed
cup test will usually give a lower flash point value and, unless otherwise indicated, the flash points
appearing in the table are closed cup values.
Flammability limits
A flammable gas or vapour will only burn in air if the composition lies between certain limits. If too much
or too little fuel is present, burning will not take place; the mixture is said to be too lean or too rich.
These limits are referred to as the lower and upper limits of flammability. The lower limit is defined s the
lowest concentration of fuel that will just support a flame. The upper limit is defined as the highest
concentration of fuel that will just support a flame. The flammability range is sometimes referred to as
the explosive range.
Auto ignition temperature
When a substance is heated to a point where it will ignite without the application of an external flame, it is
said to have reached its auto-ignition or self-ignition temperature.
Vapour density
The vapour density is the ratio of the mass of a given volume of gas or vapour to the mass of an equal
volume of another gas at the same temperature and pressure.
The mass of the vapour or gas is conveniently expressed as being relative to the mass of air, which is
taken as 1. This plus the vapour pressure of the liquid will influence the type of ventilation needed.
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Reference
FPA(UK) publication Fire & Related Properties of Industrial Chemicals
The assistance of National Chemical Products Ltd in selecting the listed chemicals is gratefully
acknowledged.
Published by
Fire Protection Association of Southern Africa
(Incorporated Association not for Gain)
(Reg. No. 73/00022/08)
P O Box 15467, Impala Park, 1472
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