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How Many Fire Extinguishers Do I Need?

The basic requirement for fire extinguishers (Class A fire risks) of a building is calculated by multiplying the area of a building’s floor space in square metres by 0.065. For example, if a single floor building is 20m x 10m you would have a floor area of 200 square metres. Multiply this by 0.065 and you arrive at the number 13. You now know that the fire extinguisher provision has to be 13A or higher. However, the actual minimum Class A provision per storey is 2x A-rated extinguishers with a combined rating of at least 26A! Once you have determined what rating you require you can select your extinguishers. If you are required to provide eg 26A, you would have to pick extinguishers with a total Class A rating of 26A or larger. Extinguisher’s ratings are advertised with the extinguishers and vary from brand to brand.

Example: if your building is 600 square metres your minimum requirement for Class A fire extinguishers would be 39A (600 multiplied with 0.065 = 39). This could for example be covered by two 6ltr water fire extinguishers (with additives) with 21A rating each.

On top of this you would need to account for any specific risks that your building contains by considering a few questions (risk assessment):

  1. Is there an area of your building that is used to store flammable liquids (for this you would need a Class B rated extinguisher to cover the risk)? A building which contains for example 50 ltrs of flammable liquid (eg Diesel), would require a Class B rating of more than 50B. You could in such a case consider foam fire extinguishers instead of the above mentioned water extinguishers, as foam extinguishers cover both Class A and Class B risks. For example 2x 6l foam extinguishers might give you a total rating of 42A and 288B (depends from the make of the extinguisher).
  2. Where is the mains power distribution board located you may want to include a CO2 extinguisher, although foam extinguishers, if tested to 35kV, and dry water mist extinguishers might also be used.
  3. Does the building have a kitchen area and if so what appliances are located there (for electrical appliances you may want to include a dry water mist or CO2 extinguisher and if you have a deep fat fryer you need to install a Class F wet chemical extinguisher or a dry water mist extinguisher)?

There are many other aspects of fire safety that need to be considered when provisioning for fire extinguishers:

Extinguishers located on the same floor of a building or across all floors if it is a single occupancy should all have a similar method of operation and should be of a similar design and standard. Therefore, EN3 extinguishers, which are red with a colour bar indicating the type of extinguisher, should not be mixed with older BS5423 extinguishers, where the whole body is coloured to indicate the type of extinguisher). Extinguishers located on different floors should be located in a similar place to make it easier to locate them in an emergency.

The user should not have to travel more than

30m for Class A and C risks

10m for Class B and F risks

to the nearest suitable fire extinguisher. Extinguishers should be located on escape routes, near to room exits, next to final exits, in corridors etc.

The Regulatory Reform Order 2005 states that a person in control of a building must carry out a fire risk assessment, part of which is the provisioning of fire fighting equipment. The person in control of the building might want to outsource this to a trained individual who can perform the risk assessment and indicate the correct provisioning for the building. Safelincs is happy to carry out extinguisher site surveys which are free of charge if you order the required fire extinguishers from us.