How many Fire Extinguishers
do I need?

There are over 15,000 (Home Office figures 2016/2017) commercial fires in the UK each year, demonstrating the importance of taking fire prevention measures on business premises.

So, what are the legal obligations of building or business owners regarding fire extinguishers?

All fire safety legislation in England and Wales for non-domestic premises is covered by the Regulatory Reform (Fire Safety) Order 2005 (RRO), which states that appropriate fire-fighting equipment, including portable fire extinguishers, must be provided where there is any risk of fire.

The RRO states that business owners and managers as designated Responsible Persons (RP) are responsible for carrying out a fire safety risk assessment and implementing and maintaining a fire management plan.

Carrying out a fire risk assessment will determine the type and number of fire extinguishers required. The fire risk assessment takes into account the nature of your business and will help you identify all the specific risks that exist, factor in any other systems already present like sprinklers or automatic suppression systems, and then identify all the specialist firefighting equipment and the particular types of fire extinguishers that will be required.

The following information is provided for general guidance purposes for workplaces. Fire extinguishers are ‘rated’ on their ability to extinguish test fires. In the case of Class A (which is plastics, wood, paper, straw, coal, textiles, furniture, etc. and carbonaceous material), a wooden crib of a specific size and length is ignited, and the amount of burning crib that can be extinguished is measured. Traditionally, the ‘basic’ extinguisher for general use is the red 9-litre water, which can extinguish 1.3m of the standard wooden crib fire, and is therefore rated 13A (the decimal point is dropped). Ratings are marked on extinguisher bodies, e.g. 13A for 9-litre water, 144B for a 6 litre AFFF. British Standard 5306 contains formulae for calculating the number of Class A extinguishers. The calculation can be simplified by applying the rule of thumb that one 13A extinguisher covers 200 square metres of floor area. To calculate how many 13A extinguishers are required, divide the floor area by 200, and round up. Example: floor area 1300 square metres: 1300 ÷ 200 = 6.5 Round up to 7, 7 x 13A water-based extinguishers. There should be a minimum of 2 extinguishers per floor unless the upper floor area is very small, i.e. below 100m2, and in single occupancy, in which case, only one extinguisher is required on the upper floor. This may be reduced by risk assessment in a sprinklered building or where automatic suppression has been fitted. Where it is desirable to have smaller, lighter extinguishers, foam or water with additives can be used to reduce weight whilst maintaining firefighting 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 (such as petrol, diesel, oils, turpentine, paraffin, paint, ethanol, methanol, etc.), C (such as propane, butane, methane, natural gas, hydrogen, etc.), D (fuelled by ignited metals such as magnesium, aluminium, lithium, titanium, potassium, etc.) and F (such as fats, cooking oils, grease, etc.), e.g. foam, carbon dioxide or powder.

However, the UK fire extinguisher regulations BS 5306-8 2012 update recommends a minimum of two Class A fire extinguishers on every floor of a building are needed unless the premises are very small, in which case one may be acceptable. Three- or six-litre foam, or nine-litre water, are the most frequently found types, although others are likely to be needed as well, most commonly CO2 extinguishers for electrical fires.