Foam fire extinguishers can be used on Class A and Class B fires. These extinguisher types work by effectively smothering the burning liquid or combustible with foam, cutting off oxygen and extinguishing the fire.
Foam fire extinguishers are also referred to as AFFF foam fire extinguishers, AFFF fire extinguisher, or spray foam fire extinguisher. AFFF stands for Aqueous Film Forming Foam.
Besides CO2 extinguishers, foam fire extinguishers are amongst the most common in use today. However, they only work on certain types of fire, and incorrect usage could spread a fire rather than extinguish it.
Find the Right Foam Fire Extinguisher
How Do Foam Fire Extinguishers Work?
Foam fire extinguishers are more effective than water fire extinguishers, as not only does the foam cool the fire, but it also cuts off its oxygen supply.
The foam released by this fire extinguisher is made up of film-forming fluoroprotein, film-forming foam, alcohol-resistant foams, air, and water.
Once sprayed onto the burning materials, the foam first cools the flames and brings the temperature down, which makes extinguishing easier.
Next, the foam then forms on top of the burning materials, cutting off oxygen, and eventually extinguishing the fire completely. When used on liquid fires, the foam floats on top of the burning liquid, making it easy to extinguish the fire.
What Is A Foam Fire Extinguisher Used For?
A foam fire extinguisher is often a necessity for buildings that are at risk of material fires involving solid materials, such as textiles and wood.
They’re also recommended for fires involving flammable liquids, such as gasoline and kerosene.
Like all fire extinguisher types, a foam fire extinguisher is used primarily for controlling a somewhat limited fire. It cannot be relied upon to reduce the extent of an out-of-control fire.
Where can foam fire extinguishers be used?
A foam fire extinguisher can be found in a wide number of business premises, residential properties, and factories. A minimum of two Class A extinguishers per floor is a requirement for all UK businesses.
You can often find a foam fire extinguisher alongside a CO2 extinguisher, particularly in such premises as:-
- Hostels
- Garages
- Factories
- Offices
- Warehouses
Foam fire extinguishers are available in several different sizes, including 2, 3, 6, and 9 litres. 6 litres in the most common size of foam fire extinguisher you’ll likely come across. The size is often determined based on the fire risk level of the premises.
What Type Of Fire Is A Foam Extinguisher Used For?
Foam fire extinguishers should only be used for Class A and Class B fires. As a last resort, they can be used for electrical fires, although it is not recommended.
Class A fires
Class A fires are fueled by common household and office materials, such as wood, paper, textiles, and certain plastics.
These combustibles are all mostly organic solids and feature some degree of carbon. Class A fires happen more frequently than all other fire classes.
The best extinguishers for Class A fires are water or monoammonium phosphate.
Class B fires
Flammable liquids cause Class B fires. Common flammable liquids include gasoline, kerosene, grease, alcohol, oil, ether, diesel, and petroleum-based oils and paints.
Class B fires most commonly occur in industries that make or frequently use paints, fuels, or lubricants. Foam fire extinguishers work best at extinguishing Class B fires, but they can also be put out by smothering.
What Not To Use Foam Extinguishers For
Foam fire extinguishers should be considered off-limits for:
Electrical fires
Electrical fires are often started by old electrical equipment malfunctioning or faulty electrical plugs. Combustible materials involved include wiring and electric panels.
Unless you can safely disconnect the electrical current (or if your foam fire extinguisher is 35000 Volt tested), you should not use a foam fire extinguisher on an electrical fire.
Still, even if you have disconnected the electrical equipment and the extinguisher is volt tested, you still risk getting an electric shock.
Carbon dioxide fire extinguishers are the best option for electrical fires.
Class C fires
Class C fires are caused by combustible gases, including propane, methane, butane, and natural gas. These fires are highly explosive and, therefore, one of the most dangerous fire types.
This fire type is commonly started by a gas leak or faulty industrial equipment. The only safe way to extinguish a Class C fire is by using a dry powder extinguisher.
Class D fires
Class D fires involve combustible metals, including potassium, magnesium, titanium, and aluminium. Although large pieces of these metal types are not highly flammable, small shavings are.
Class D fires most commonly occur in factories or production lines that work with these metal types.
The best way to extinguish a Class D fire is an L2 metal powder extinguisher.
Class F fires
If you cause a fire while cooking, it is most likely a Class F fire. These are fires that are caused by cooking or vegetable oil, which are both highly flammable.
Deep fat frying is the biggest cause of cooking fires but can be caused by a variety of reasons, such as unattended pots and pans.
Class F fires such as chip pan fires can be smothered if small enough, or by using a wet chemical fire extinguisher if too big to be smothered. You should never use water on a Class F fire, as this will spread the fire.
Given that foam fire extinguishers primarily use water, using one on a Class F fire would worsen the fire rather than extinguish it.
What Colour Is A Foam Fire Extinguisher?
Like all other fire extinguishers, a foam fire extinguisher has a red cylindrical pressure vessel.
To distinguish a foam fire extinguisher from the other types, look for the cream-coloured label at the top, which should read ‘FOAM’ in big, red letters.
The pressure vessel should also have an extinguisher, which will read ‘FOAM EXTINGUISHER’.
The Pros And Cons Of Using A Foam Fire Extinguisher
Although foam fire extinguishers are recommended for all business premises and residential properties, there are a few pros and cons of the extinguisher type that are worth considering.
These include:
Pros:
- Foam is a safe and non-toxic substance
- Foam does not damage surfaces (although this cannot be guaranteed)
- It smothers the fire, which reduces the threat of it reigniting
- Although it is not recommended for electrical equipment-related fires, if the foam does accidentally gets on combusted electrical gear, it will most likely be safe
- Most foam fire extinguishers are lighter than water fire extinguishers
Cons:
- Cannot be used on Class, C, D, and E fires (in a lot of cases, a foam fire extinguisher will make these fires worse)
- Can freeze if kept in unsuitable conditions
- More expensive than a water fire extinguisher
- If used on electrical equipment, the electrical equipment will likely be damaged
How To Use A Foam Extinguisher
The way you use a foam extinguisher depends on the type of fire you’re extinguishing. However, regardless of the fire, the first thing you do in every instance is to remove the safety pin.
When extinguishing flammable liquid fires and flammable solid fires, never spray directly at the flames. Instead, follow these steps:
Step 1: Aim the foam fire extinguisher hose at the base of the flames, where the burning liquid or solid combustibles are. Keep the fire extinguisher itself on the floor at all times and a safe distance away from the fire itself.
Step 2: Squeeze the lever in order to release the foam. The aim is to smother the fuel at the bottom entirely, cutting off the oxygen supply. Sending foam over the flames would be futile and could even worsen a liquid fire.
Step 3: Continue for as long as it takes to extinguish the fire. Use the whole contents of the extinguisher if necessary. Each fire is case-specific, but you should be able to tell when you’ve done enough when the flames are out.
Although it is not recommended, if you do have to use a foam fire extinguisher to contain an electrical fire, make sure to keep yourself a safe distance away from the fire – at least 1m. This will reduce the risk of you suffering from electrical shocks.
Final Thoughts
Foam fire extinguishers should be part of any business’s fire control equipment, especially for industries that regularly work with textiles, light plastics, paper, and wood, liquid flammable gases such as gasoline, diesel, and ether, or oil.
Although AFFF foam extinguishers are unsuitable for Class C, D, and F fires, they provide a solution to multiple fire risks and are more effective than water fire extinguishers.
Further Reading
- Fire extinguisher regulations UK – more information on legal requirements for fire extinguishing equipment in the work environment.
