Foam Fire Extinguishers

Foam fire extinguishers are commonly used in commercial and public buildings where fires involving solid materials or flammable liquids may occur. They work by smothering flames and cooling the burning material, helping to prevent re-ignition.

What Are Foam Fire Extinguishers Used For?

Foam fire extinguishers are primarily designed for:

• Class A fires – involving solid combustible materials such as wood, paper, cardboard, and textiles
• Class B fires – involving flammable liquids such as petrol, diesel, paint, and solvents

This makes foam extinguishers suitable for environments where both solid materials and flammable liquids are present.

Where Can Foam Fire Extinguishers Be Used?

Foam fire extinguishers are commonly installed in:

• Offices
• Schools and colleges
• Retail premises
• Warehouses
• Hotels
• Residential blocks (common areas)
• Premises storing flammable liquids

They are often selected where a single extinguisher needs to cover more than one fire risk.

Where Can Foam Fire Extinguishers Not Be Used?

Foam fire extinguishers must not be used on:

• Class C fires – involving flammable gases such as propane, butane, or methane
• Class D fires – involving combustible metals such as magnesium or aluminium
• Class F fires – involving cooking oils and fats (e.g. chip pan fires)
• Live electrical fires, unless the extinguisher is specifically tested and certified for electrical use

Standard foam extinguishers are water-based and may present an electrocution risk if used on energised electrical equipment. Always isolate the power supply first if it is safe to do so.

How Do Foam Fire Extinguishers Work?

Foam extinguishers work by:

• Creating a blanket over the fire, separating the fuel from the oxygen
• Cooling the burning material, reducing the risk of re-ignition

When used on flammable liquid fires, the foam floats on the surface, sealing vapours and suppressing flames without splashing the fuel.

Cooling and AFFF Foam Action

Foam fire extinguishers work in two principal ways:

Firstly: Being chiefly water-based, they help to cool the burning material, reducing the temperature below ignition point.

Secondly: Aqueous Film Forming Foam (AFFF) creates a film over the surface of the fire, which separates the fuel from oxygen and suppresses flammable vapours — particularly effective on liquid fires.

This dual action helps reduce the risk of re-ignition.

How Do You Identify a Foam Fire Extinguisher?

You can identify a foam fire extinguisher by:

• Its red body with a cream-coloured label, marked “FOAM”
• An accompanying extinguisher ID sign stating its approved fire classes

Are Foam Fire Extinguishers Safe for Electrical Fires?

Most standard foam fire extinguishers are not suitable for use on live electrical equipment, as they are primarily water-based.

However:

• Some modern foam fire extinguishers are independently tested and certified for limited electrical use up to a specified voltage
• This will always be clearly stated on the extinguisher label and in the manufacturer’s certification

Never assume electrical suitability. Always check the extinguisher label or seek professional fire safety advice before use.

What Are Foam Fire Extinguishers Also Known As?

A foam fire extinguisher can also be known by one of the following names:

• AFFF foam fire extinguisher
• AFFF fire extinguisher
• Spray foam fire extinguisher

The term “AFFF” refers to Aqueous Film Forming Foam, which describes how the extinguishing agent works.

What Are the Pros and Cons?

Pros

Several pros exist with the use of a foam fire extinguisher, these are listed as follows:

• Effective on both Class A and Class B fires
• Reduces the risk of re-ignition
• Less residue than dry powder extinguishers

Cons

• Not suitable for gas, metal, or cooking oil fires
• Potential electrical risk if used incorrectly
• Water-based, so freezing conditions may affect performance

Who Needs Foam Fire Extinguishers?

Foam fire extinguishers are considered a good choice for general-purpose fire protection and are suitable for many business premises where more than one fire risk may be present.

Examples include:

• Hostels
• Garages
• Factories
• Offices
• Warehouses

They are commonly selected where both Class A and Class B fire risks exist.

How Do You Use a Foam Fire Extinguisher?

The type of fire will determine how the extinguisher should be used.
However, all scenarios share the same first step:

FIRST STEP (all scenarios):

Remove the safety pin to break the anti-tamper seal and stand at a safe distance.

For Flammable Liquid Fires (Class B):

• NEVER spray directly into the liquid, as this may cause the fire to spread
• If the liquid is contained, aim at the inside edge of the container
• If the liquid is not contained, use a gentle sweeping motion over the top of the fire
• Alternatively, if a nearby surface is available, spray onto that surface so the foam flows onto the fire

This allows the foam blanket to settle over the burning liquid and suppress vapours safely.

Foam Fire Extinguishers and UK Fire Safety Law

UK fire safety legislation does not mandate specific extinguisher types.
Under the Regulatory Reform (Fire Safety) Order 2005, the Responsible Person must provide appropriate fire-fighting equipment based on the findings of a fire risk assessment.

British Standard BS 5306-8 provides recognised guidance on the selection, positioning, and maintenance of foam fire extinguishers.

Our Services

If you need fire extinguisher servicing and maintenance, our accredited consultants will attend your sites at a time convenient to you. Contact us today to arrange a visit and decide on the future course of action.