Fire Extinguisher Types and Fire Classes

Type	Class A	Class B	Class C	Class D	Electrical	Class F
	Solid combustibles (such as wood, paper & textiles)	Flammable liquids (such as petrol, diesel & paraffin)	Flammable gases (such as methane, propane & hydrogen)	Flammable metals (such as magnesium, aluminium & lithium)	Electricals (such as computers & electric heaters)	Cooking oil (such as deep fat fryers & chip pans)
Water					Only if di-electrically tested
Water Mist						*
Carbon Dioxide (CO2)
ABC Powder
Wet Chemical		Sometimes
AFFF Foam					Only if di-electrically tested

Fire Classification

 

CO2 fire extinguishers

How to identify a CO2 fire extinguisher

CO2 fire extinguishers are identified by their black label and usually have a frost-free horn that protects the user from freeze-burns when discharged. 

What type of fire can I use a CO2 extinguisher on?

• Fires involving electrical equipment
• Flammable liquids (class B)

They are predominately used on fires involving live electrical equipment, as CO2 is not a conductor. In addition, CO2 extinguishers don’t leave behind any harmful residue so can often be discharged on expensive electrical equipment without causing damage. They were originally designed for use on flammable liquid fires and therefore many have a class B fire rating.

Don't use on: Solid combustibles due to a risk of re-ignition.

Where can a CO2 extinguisher be used?

• Server rooms
• Any room containing a large amount of large electrical equipment 

CO2 extinguishers are also commonly found in offices, warehouses, schools or retail premises paired with water of foam extinguishers. They have traditionally been specified to cover electrical fire risks in these locations but as there are now extinguishers that are both di-electrically tested and cover class A risks, this pairing is not usually necessary.

CO2 extinguishers contain only carbon dioxide gas and care should be taken when discharging them as there is a risk of asphyxiation if used in confined spaces. Frostbite can also occur if the discharged CO2 comes into contact with the users skin (the frost-free horn is designed to prevent this).

How to CO2 extinguishers work?

CO2 extinguishers work by cutting off the oxygen supply from the fire and effectively suffocating it. CO2 extinguishers can pose a risk of re-ignition as they are not effective as a coolant in the way that water is, and if discharged on class A or class F fires, could actually make the fire worse.

Fire Classification

 

Dry powder fire extinguisher

How to identify dry powder extinguishers

Dry powder extinguishers have a blue label and will feature the word 'Powder' on the front.

What type of fire can a dry powder extinguisher be used on?

They are versatile and can be used on:

• Solid combustibles eg. Wood, coal, paper, fabric etc.
• Flammable liquids eg. Petrol, oils, paint, alcohol, parafin etc.
• Flammable gases eg. Propane
• Fires involving live electrical equipment

Where can a powder extinguisher be used?

• Construction sites
• Garage forecourts
• Vehicles & machinery

Powder extinguishers are ideally suited to outdoor locations as there is a risk of inhalation when discharging them indoors. They are also difficult to clean up when discharged and can cause damage to soft furnishings. 

How do powder fire extinguishers work?

Powder extinguishers (also referred to as dry powder or ABC powder) contain mono-ammonium phosphate which is mixed with other powders. They work by smothering the fire which creates a barrier between the fuel and the oxygen. 

Fire Classification

 

Wet chemical extinguishers

How to identify a wet chamical fire extinguisher

Wet chemical fire extinguishers (also known as class F extinguishers) have a yellow label and are designed specifically for use on fires involving combustible cooking media such as burning oil and fat.

What type of fire can I use a wet chemical fire extinguisher on?

• Solid combustibles eg. Wood, coal, paper, fabric etc. (class A fires)
• Cooking oils and grease (class F fires)

Some are also designed for use on class B fires (petrol, diesel, paint, paraffin etc) and fires involving live electrical equipment as indicated on the front of the extinguisher body.

Dont use on: Class C (flammable gases) and class D (flammable metals) fires.

Where can a wet chemical fire extinguisher be used?

• Commercial kitchens
• Deep fat fryers

How do wet chemical fire extinguishers work?

Containing potassium salts, these extinguishers work by creating a soapy barrier between the fire and the oxygen. This cools the fire and prevents reignition. This type of extinguisher has a special lance applicator nozzle that allows the user to gently dispense the media from a suitable distance. Normal water-based extinguishers with large droplets would cause an 'explosion' of steam and carry burning oils and fats from the container. Equally, a CO2 extinguisher's jet would carry burning oil out of the container and also would have insufficient cooling effect to stop re-ignition.

Fire Classification

 

Foam fire extinguishers

Foam fire extinguishers are identified by their cream label and are designed for class A and B fires plus in some cases fires involving electrical equipment. There are a number of different types of foam fire extinguishers and some are now classified as hazardous to human health and the environment. Foam extinguishers are water-based and contain chemicals that form a ‘frothy agent’. The foam cools and smothers the fire, extinguishing it and preventing reignition.

Foam extinguisher uses

• Offices 
• Schools 
• Shops
• Hospitals
• Public buildings

AFFF foam

This type of foam extinguisher contains toxic fluorine compounds (PFAS) which is harmful to humans and the environment. AFFF foam extinguishers are due to be phased out by law from 2025 and Safelincs have taken the decision to discontinue the sale of this type of extinguisher.

AFFF foam extinguishers are commonly found in many premises across the UK including offices, schools, warehouses, shops and public buildings. The disposal of this type of media is tightly controlled due to its harmful nature.

Fluorine-free foam

Recently, manufacturers have begun to replace AFFF foam extinguishers with fluorine-free foam extinguishers. This type of fire-fighting foam is versatile in application but is a more environmental choice, being free from the harmful PFAS chemicals contained in AFFF foam. Fluorine-free foams can be used on class A and B fires as well as being di-electrically tested for use on electrical equipment.

Fire Classification

 

Service-Free Fire Extinguishers

P50 extinguishers are a relatively new type of fire extinguisher and provide an alternative to steel extinguishers that are more durable and easier to maintain. With a plastic outer casing and super-strong inner core, this type of extinguisher will not corrode and does not require annual servicing from an external technician. With twice the lifespan of a traditional steel extinguisher, P50 service-free extinguishers are 100% recyclable and offer an environmental option. They have a low-carbon manufacture process and offer significant cost savings over their long lifespan.

P50 extinguishers are available in a range of media including water mist and eco-foam. They have a 10-year warranty and excellent fire-fighting capability. Find out more about this type of extinguisher on our P50 information guides. 

 

Still not sure which type you need?

Read our extinguishers by location and extinguishers for vehicles guides for help choosing the correct extinguishers for your requirements.

Or, contact our friendly team on 0800 612 6537 or email support@safelincs.co.uk for help choosing a suitable extinguisher for your location.