Calculating your requirements

Effectively calculating your fire and safety requirements.

How do we identify the quantity extinguishers you need?

Please note that this section is only provided for guidance only and we would strongly recommend that a qualified fire engineer visits your premises to identify the types and quantities of fire extinguishers required.

It is generally considered that all types of premises will have Class A materials present. So, this is used to calculate the minimum quantity of portable fire extinguishers required. Where specific risks such as fuel and electric switchgear are also present additional extinguishers will be required.

British Standard 5306-8:2012 specifies that the minimum quantity of extinguishers with an A rating should be calculated as follows:
(a) For any storey with a floor area less than or equal to 400m2, there should be at least two extinguishers with a class A rating and having a combined minimum total fire rating of 26A;
(b) For any storey with a floor area exceeding 400m2, there should be at least two extinguishers with a class A rating and having a minimum total fire rating of 0.065 x floor area of the storey (in square metres).

Examples of calculation
If we take a warehouse that has 1000m2 in floor area and with a small 2 storey office area covering 150m2 attached to the front of it, there would be a minimum requirement of: Ground floor: 0.065 x 1150 = 75A and1st floor: Less than 400m2 = 26A

If we take a standard 6-litre water extinguisher having a rating of 13A then we would require the following number of extinguishers: 
Ground floor: 75A ÷ 13A = 6 extinguishers
1st floor: 26A ÷ 13A = 2 extinguishers


Please note: Halon fire extinguishers were banned from general use by the Montreal Protocol and as of December 2003. They can only be used by certified users such as the Armed Forces and the Aviation Industry.

It should be noted that many extinguishers are dual rated so whilst covering a specific issue, it will also contribute towards the total A rating. For instance, a standard 6-litre wet chemical extinguisher which has a rating of 13A/75F would cover 0.11m2 of class F risk as well as contributing 13A towards the overall A rating, effectively reducing the total quantity of water extinguishers required by one. Extinguishers should be easily available near the fire hazard concerned, but not so near as to be inaccessible or place the operator in undue danger. 

Normally extinguishers should be located:
  • In clearly visible positions on brackets, floor stands or within cabinets
  • Where they would be readily seen by persons following an escape route
  • Near to room exits, corridors, stairways, lobbies and landings
  • Ideally at similar positions on multi-floor premises, so that extinguishers covering specific risks are reached first by a prospective user

The maximum travel distance from the site of the fire to an extinguisher can be: 
  • Class A or C fire risks = 30 metres
  • Class B, F or electrical fire risks = 10 metres
  • Class D = on a case by case basis by expert advice
If you have any concerns over the quantity, types or serviceability of the fire extinguishers at your workplace then our team of experts at Fire Link Fire and Safety Services can provide free advice. 
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