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5 Apr, 2023

Foam fire extinguishers are used on Class A and Class B fires. They work by stifling flammable liquid fires or flammable solids with foam to cut off the oxygen supply and extinguish the flames.

There are five main types of fire extinguishers, each further classified into categories. These are foam, water, dry powder, CO2 and wet chemical.

In terms of foam, there are a further five types of fire extinguishers, which are Alcohol-Resistant Film-Forming Fluoroprotein (AR-FFFP), Fluoroprotein Foam (FP), Alcohol-Resistant Fluoroprotein Foam (AR-FP), Regular Protein Foam (P) and Film-Forming Fluoroprotein (FFFP) foam extinguishers.

Foam fire extinguishers, also known as Aqueous Film-Forming Foam (AFFF) extinguishers, are only suitable for putting out certain fire types. In this guide, we’ll be covering everything you need to know about foam fire extinguisher use, how they work, and more. Afterwards, you should be in a position to make an informed choice on whether you should have a foam fire extinguisher in your home or workplace.

What Are Foam Fire Extinguishers Used For?

Buildings containing textiles, wood and other flammable solids, which can cause Class A fires, will likely require at least one foam fire extinguisher.

It’s also advisable to have a foam extinguisher handy if you’re using or storing flammable liquids. Petrol, kerosene, diesel, alcohol, and certain oils and greases can cause Class B fires, which foam fire extinguishers can also be used to tackle.

A foam fire extinguisher will usually extinguish fires involving burning liquid or flammable solids that aren’t yet out of control. You should never rely on any type of fire extinguisher to put out runaway fires that have already gained the upper hand on extinguishers.

Foam fire extinguishers are found in numerous factories, business premises and residential properties. All UK businesses are required by law to contain a minimum of two Class A extinguishers on every floor of their premises.

Factories, offices, warehouses, garages and hostels are among locations where both foam fire extinguishers and CO2 fire extinguishers are often found housed together.

Foam fire extinguishers come in several sizes, with a 6-litre foam extinguisher being the most common. The size of an on-site foam fire extinguisher is often determined by the fire risk level of the site itself. Foam extinguishers also come in 2-litre, 3-litre, and 9-litre containers.

How Foam Fire Extinguishers Work

Foam fire extinguishers are more effective ways of dousing limited flames than your average water fire extinguisher. With a foam extinguisher, the Aqueous Film-Forming Foam goes some way to cooling the fire while also cutting off its oxygen supply.

This fire extinguisher foam comprises a mixture of Film-Forming Fluoroprotein, alcohol-resistant foams, film-forming foams, water and air. These counteract fires involving flammable solids and many burning liquids.

When you spray the foam onto the fire, it spreads over the flames to cool them and cut off their oxygen supply. By cutting off its oxygen, the fire can no longer sustain itself which causes it to die. With burning liquid fires, the foam from the AFFF fire extinguisher actually floats on the surface of the liquid. This action cools the liquid and makes extinguishing the fire easier.

Advantages of Foam Fire Extinguishers

Foam fire extinguishers are often used to control fires in both residential and business properties. They have a number of advantages, including:

  • Safe for use: Aqueous Film-Forming Foam is non-toxic and hence safe for human use.
  • Won’t make electrical fires worse: Even though foam extinguishers are not very effective or recommended for use on electrical fires, they are unlikely to cause the flames to intensify if sprayed directly onto combusted electrical appliances.
  • Lower chance of damage: Foam from a foam fire extinguisher won’t likely cause damage to surfaces, although this cannot be guaranteed.
  • Reduced chance of re-ignition: Foam fire extinguishers smother fires, meaning that chances of a fire re-igniting are minimal.
  • Easier to use: A foam fire extinguisher is likely lighter than its water equivalent.

Disadvantages of Foam Fire Extinguishers

Although the advantages of a foam fire extinguisher are plentiful, there are also certain disadvantages attached to a foam extinguisher. These are:

  • Not for Class C fires: Foam fire extinguishers work on Class A or Class B fires. Using a foam extinguisher on Class C to E fires could increase the volatility of any existing flames.
  • Not suitable for use on electrical appliances: If you use foam fire extinguishers on electrical appliances experiencing electrical fires, it’s likely that the result could be negative. The chances are the fire will not be extinguished and the electrical appliances could be permanently damaged.
  • Can’t be stored in cold places: A foam fire extinguisher could freeze if it is kept in conditions that are too cold.
  • More expensive: A foam extinguisher will cost you more than a water fire extinguisher.

Maintenance and Inspection

A foam fire extinguisher should be inspected and go through a basic service once annually in accordance with BS 5036-3. A third-party accredited fire extinguisher technician should carry out the inspection.

Regulations and Standards

Foam fire extinguishers are regulated under the British Standards 5306 Part 3. According to BS 5036-3, you should test foam fire extinguishers on a five-yearly basis by discharge. You must refill or replace them at least once every decade.


There are different ways to use a foam extinguisher. Experts advise varying techniques of use depending on the type of fire you’re extinguishing. One fundamental step never changes though: always remove the safety pin before you do anything else!

After removing the foam extinguisher safety pin, follow the next steps to extinguish the fires you should be using foam extinguishers for. These are Class A and Class B fires that involve flammable solids and flammable liquids.

Remember to never aim a foam fire extinguisher directly at the flames when you extinguish flammable liquid fires or those that involve flammable solids. Rather, point the foam extinguisher hose towards the fire’s base where the burning liquid or combusting solids are. Don’t pick the foam fire extinguisher up; rather let it sit on the floor’s hard surface.

Make sure you’re at a safe distance from the blaze when releasing the foam by squeezing the lever on the foam extinguisher. You want to saturate the base of the fire with foam, covering it totally to cut off the fire’s supply of oxygen to smother it.

If you aim the fire extinguisher to spray foam over the top of the blaze, you’re wasting your time. In fact, with certain flammable liquids involved, you could end up making the fire worse.

Empty the extinguisher entirely if you need to. Your primary aim is to put out the fire, not to conserve the contents of the foam extinguisher so carry on spraying foam until the flames are gone. Because of the coating of foam, there’s very little chance of a fire re-igniting.

You shouldn’t, as a rule, try to extinguish electrical fires using a foam fire extinguisher. Sometimes, though, it may be the only way to contain the blaze. If you are going to use a foam fire extinguisher in this instance, keep at least one metre away from the fire while spraying. This way, the chances of ending up being electrocuted are significantly reduced.


You should store a foam fire extinguisher in an easily-accessible, cool and dry place with decent ventilation. Excessively high temperatures could lead to the decomposition of the carbon dioxide element. If this happens, the fire extinguisher will stop working. In winter, make sure the foam extinguisher isn’t too cold or its contents could freeze.


Employers in the UK have a legal obligation, as per The Regulatory Reform (Fire Safety) Order of 2005, to inform about, instruct on and provide fire training to their employees in regard to workplace fire precautions. Training in the use of foam fire extinguishers for flammable liquids and solids forms part of this training.

At MCFP, we’re here to assist you with all your fire protection needs. These include all your business risk assessment and fire training for you and your employees. Contact us for more information, along with everything involving your fire extinguisher requirements.