Number of Fire Extinguishers Required
The following information is provided for guidance purposes,
and should not be relied upon for the purposes of a fire risk
assessment, in which case, British Standard 5306-8:2000 should
be referred to.
extinguishers for use on class A fires (flammable solids
such as paper, wood, textiles etc) are ‘rated’ on their ability to extinguish
The test rating can be found on the extinguisher label, e.g.
13A, 21A, 26A etc. Similarly, extinguishers for use on flammable
liquids are given a class B rating e.g. 34B, however the
calculation for these is different and is not covered here.
Class 'A' extinguishers
British Standard 5306 contains formulae for calculating the
number of class A extinguishers as follows:
floor area (m2) x
0.065 divided by the extinguisher rating and round up.
e.g. For a floor area of 1250 m2:
extinguishers: 1250 x 0.065 ÷ 13 = 6.25
Round up to 7
extinguishers: 1250 x 0.065 ÷ 21 = 3.87
Round up to 4
(As a rule of thumb one 13A extinguisher covers 200 square
metres of floor area)
There should be a minimum of 2 extinguishers per floor with a
combined rating of at least 26A,
unless the upper floor area is very small i.e. below 100m2,
and in single occupancy, in which case, only a minimum rating of
13A is required on the upper floor.
extinguishers should be positioned close to exits, for further
information on siting see: siting
Where it is desirable to have smaller, lighter extinguishers,
foam, or water with additives can be used to reduce weight
whilst maintaining fire fighting capability. e.g. 6 Litre AFFF
foam spray extinguishers are usually rated at 13A, but are
approximately 30% lighter than 9 litre water.
Specialised extinguishers should also be provided to cover
classes B (Liquids), D (Metals), E (fires involving electrical
apparatus) and F (cooking oils and fats), e.g. foam, carbon
dioxide or powder.
office environment we recommends the relevant number of 6L (or
3L) AFFF extinguishers plus an appropriate amount of CO2
extinguishers to cover any electrical risk.