Effectively calculating your fire and safety requirements

How do we identify the quantity of extinguishers you need?

Please note that this section is only provided for guidance 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 needed.

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 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 × floor area of the storey (in m²)

Examples of Calculation

If we take a warehouse that has 1000m² in floor area 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 × 1150 = 75A and First Floor: Less than 400m² = 26A

If we then take a standard 6 litre water extinguisher, having a rating of 13A, we would need the following number of extinguishers:

Ground Floor: 75A ÷ 13A = 6 extinguishers and First Floor  26A ÷ 13A = 2 extinguishers

Please note: Halon fire extinguishers were banned from general use by the Montreal Protocol as of December 2003. They can only be used by certified users, such as the Armed Forces and the Aviation Industry. It should also be noted that many extinguishers are dual rated, so while covering a specific issue it will also contribute towards the total A rating.

Normally extinguishers should be located:

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