How to choose the correct fire extinguishers?

There are many types and sizes of fire extinguishers which can add confusion in selecting the correct ones. However, most premises have similar fire risks such as paper, materials and wood (Class A), electrical equipment, and kitchens.

To keep it simple and save you money, we recommend water, water additive or water mist extinguishers for most premises. These cover Class A fires and, in the UK, extinguisher selection is based on floor area and Class A fire ratings.

For most, other than high risk premises, the calculation is floor area in square metres (each floor) x 0.065. This gives the minimum Class A rating. If your floor is more than 50m2, you must have at least two Class A rated extinguishers with a combined rating of 26A or more.

Example

A two-floor office: 350m² (ground) + 300m² (first)

A standard 6-litre water extinguisher carries a 13A rating — so two per floor satisfies both the minimum rating and the two-extinguisher rule.

Total: 4 extinguishers across the building.

No one should have to travel more than 30 metres to reach an extinguisher, so position them near exits.

Placement

In addition, you need to position these for users to not travel more than 30m to reach an extinguisher. Place them by fire exits, fire alarm call points, or on exit routes while not obstructing escape or causing a hazard. Do not place near heat sources, too near the fire risk, where they can be knocked, where they can be hidden, or where they cannot be easily grabbed in an emergency.

Extinguishers must be mounted on wall brackets (always included) or on a stand (easiest).

Flammable liquids

If you store them in quantity indoors, you may want to change the water extinguisher to a foam one (powder is an option but creates a large dust cloud indoors, restricting visibility indoors with low ceilings). The precise calculations for Class B cover (flammable liquids) are complex and depend on open surface areas, distances between stored items and other criteria. If outdoors, powder is probably better and does not freeze. Due to the risks, we recommend an on site survey.

Kitchens

If you operate a kitchen area with a kettle and microwave, that is just electrical equipment. If you have a small cafe or mobile kitchen, you need a fire blanket and a small Class F extinguisher for fat fires. If you have a commercial kitchen with ranges and deep fat fryers, you probably need larger fire blankets and two 6 litre wet chemical extinguishers. You may even need a kitchen suppression system which is beyond the scope of this guide.

Note - Foam and powder are not suitable for fat fires.

Electrical equipment

This one involves some common sense as everywhere has electrical fire risks. For example, if you have large, complex electrical machines, you may need 5kg CO2 extinguishers in the vicinity - within 10m. If you have an office with standard computers and electrical equipment, a 2kg CO2 within 10m will suffice. If you use 24 hour test equipment, washers/drying and servers the risks are much higher and may need automatic suppression systems in addition to portable extinguishers.

Lithium-ion batteries

These are becoming a high risk item as Fire Services have found them very difficult to extinguish due to "thermal runaway" where one cell ignites the next and causes a chain reaction while often in a sealed box. Lithium-ion battery fires accelerate incredibly fast and give off toxic gases with an explosion risk.

In more open areas such as warehouses with charging stations for trucks, a lithium-ion fire blanket (the best and safest way to suppress) and a 6 litre specialist lithium-ion battery extinguisher may be suitable. This is also good for places where batteries can be used hard such as power tools, hire centres, construction sites. But, if in a very confined space, you should not be placing yourself or staff at risk of the toxic gasses.

Note that Class D "lithium" fires refers to the base metal Lithium (remember school chemistry labs?) and is not related to lithium batteries. Also note that you will not be able to extinguish a car battery fire so do not even try.

Signs

Although fire extinguishers have user instructions and fire class suitability, you are required to fix a compliant sign above each one to identify the location and show if it has been removed.

Maintenance

In addition to your own monthly visual inspection of each extinguisher, you are required to maintain them in accordance with the manufacturer's instructions - usually to British Standard 5306 Part 3 by a competent (qualified and insured) technician.

P50 extinguishers are designed for "self-maintenance" with built in protections and 10 year warranty (and a 20 year life) that could save a lot of money over time.