As there are different types of fire emergencies, there are also different types of fire extinguisher. Choosing the wrong extinguisher may actually feed the fire, resulting in greater damage and a significantly higher chance of injury or even fatalities.

Whoever is responsible for fire safety on your business premises, therefore needs to be able to identify and use the correct fire extinguisher for potential fire emergencies.

In this article, we explain the different classes of fire, how fire extinguisher types differ in terms of contents and application, how to choose the right fire extinguisher for your workplace, and more.

Fire classifications explained

The right fire extinguisher for any given workplace or fire emergency is always determined by the nature of the fire itself. Each fire extinguisher type is designed to douse particular classes of fire. Some may be effective against 2 or 3 different classes, but no single extinguisher is suitable for fighting all types of fires.

As such, a proper understanding of the different fire extinguisher types starts with a complete knowledge of the 6 fire classes:

Class A fires: Ordinary combustibles

• Fuel source: Common solid materials such as wood, paper, textiles, cloth, plastics, and rubbish.
• Characteristics: These fires burn with an ember and leave behind ash. They are the most common fire type in homes, schools, and offices.

Class B fires: Flammable liquids

• Fuel source: Liquids such as petrol, diesel, oils, alcohol, solvents, paints, and other hydrocarbons.
• Characteristics: These fires spread rapidly and can reignite easily if not fully smothered. Water is ineffective and may spread the burning liquid.

Class C fires: Flammable gasses

• Fuel source: Pressurised or bottled gases such as propane, butane, methane, acetylene, or natural gas.
• Characteristics: Highly explosive if gas leaks are not controlled; ignition can cause sudden flash fires.

Class D fires: Combustible metals

• Fuel source: Reactive metals such as magnesium, titanium, sodium, lithium, and potassium.
• Characteristics: Extremely high-temperature fires that react violently with water and many common extinguishing agents.

Class E fires: Electrical fires

• Fuel source: Energised electrical systems, including wiring, circuit breakers, computers, appliances, and machinery.
• Characteristics: Shock hazard in addition to fire risk. Once the electrical supply is cut, the fire usually becomes Class A, B, or F depending on surrounding materials.

Class F fires: Cooking oils or fats

• Fuel source: High-temperature cooking oils, deep-fat fryers, lard, and butter.
• Characteristics: Fires burn hotter than standard Class B fires and can violently flare up if water is used.

There are also different types of fire risk assessment. Understand how they differ and when they’re necessary in our guide to fire risk assessment types.

The Fire Triangle – and the role of fire extinguishers

The fire triangle represents the three essential elements required for a fire to ignite and sustain itself.

• Oxygen – usually the oxygen in the air (about 21%), which supports combustion.
• Fuel – any combustible material, solid, liquid, or gas, that provides something for the fire to consume.
• Heat – the energy source that raises the material to its ignition temperature. This can come from open flames, sparks, friction, faulty wiring, or hot surfaces.

 

In modern fire suppression, it may also be referred to as the fire tetrahedron (a pyramid with a triangular base), with chemical reaction being a fourth element in of itself:

 

All fire extinguishers are designed to starve a fire of one or more of the three prerequisites outlined in the fire triangle – or directly interrupt the chemical reaction responsible for the fire, as addressed by the fire tetrahedron.

If any one of the three classic elements is removed, the fire cannot continue to burn. This principle is the foundation of fire suppression. However, certain fire extinguishers can neutralise the chemical reaction causing the fire without removing oxygen, fuel, or heat from the equation.

Starving a fire of oxygen

Fire needs oxygen to sustain the chemical reactions of combustion. Oxygen molecules combine with the fuel’s carbon and hydrogen atoms, releasing heat, light, and smoke. When the oxygen supply is reduced or cut off, the chemical reaction cannot continue.

Starving a fire of fuel

Combustion can only continue if fuel is available to burn. Without fuel, there’s nothing left for the chemical reaction to consume, and the fire dies out.

Starving a fire of heat

Every fuel has an ignition temperature — the minimum heat required to sustain combustion. If the burning material is cooled below this temperature, the fire goes out because it cannot maintain the chain reaction.

Interrupting the chemical reaction

Fire is the result of a chemical reaction that continually produces free radicals that propagate the combustion process. By neutralising these reactive intermediates, the self-sustaining chemical process of combustion is halted, causing the fire to die out even though oxygen, fuel, and heat remain present.

The six main fire extinguisher types – Contents, colours, applications, and limitations

There are 6 main types of fire extinguishers used on work premises across the UK. More specialised extinguishers do exist, but all common fire classes can be combatted with one of the following standard extinguisher types.

Water fire extinguishers

Water fire extinguishers use a pressure nozzle to produce a jet of water.

• Contents: Pressurised water.
• Colour: Bright red body, label or band.
• Applications: Effective on Class A fires (wood, paper, textiles, and other organic combustibles).
• Fire triangle focus: Heat – cools the burning material below ignition temperature.
• Limitations: Must not be used on electrical fires (risk of electrocution) or flammable liquids (may spread the fire).
• Common locations: Offices, schools, shops, public buildings.

Foam fire extinguishers

Foam fire extinguishers focus primarily on smothering fires, thereby starving them of the oxygen required to sustain the chemical reaction.

• Contents: Aqueous Film-Forming Foam (AFFF) solution.
• Colour: Cream body, label, or band.
• Applications: Suitable for Class A and Class B fires (solid combustibles and flammable liquids like petrol or paint).
• Fire triangle focus: Oxygen & heat – forms a film over liquid fuels to block oxygen, while cooling the surface.
• Limitations: Not safe on chip-pan/fat fires, live electrical equipment. Alcohol-based liquid fuels and liquified gasses are also problematic for foam fire extinguishers, as these fuels can break down the foam, limiting its ability to effectively smother the fire.
• Common locations: Offices, warehouses, garages, petrol stations.

Dry chemical fire extinguishers

While often listed in the same category, there are actually two distinct subtypes of dry chemical extinguishers: ABC powder and Class D powder. Each is designed for very different fire risks.

1. ABC Powder Fire Extinguishers
   

• Contents: Fine chemical powder such as monoammonium phosphate or ammonium sulfate.
• Colour: Blue body, label, or band.
• Applications: Multipurpose — effective against Class A (solids), Class B (liquids), Class C (gases), and safe on electrical fires.
• Fire triangle focus: Fuel & oxygen – The powder interrupts the chemical chain reaction within the flames while also smothering oxygen contact.
• Limitations: Creates dust clouds that can reduce visibility, damage sensitive equipment, and irritate breathing — not ideal for offices or enclosed spaces.
• Common locations: Workshops, garages, gas storage areas, vehicles, outdoor sites.

2. Class D Powder Fire Extinguishers
   

• Contents: Specialist dry powders formulated for burning metals (e.g. sodium chloride-based or graphite-based powders).
• Colour: Also marked blue, but explicitly labelled for Class D use only.
• Applications: For Class D fires involving combustible metals such as magnesium, titanium, sodium, lithium, potassium.
• Fire triangle focus: Heat & oxygen – The powder absorbs heat and creates a crust over the burning metal, isolating it from oxygen and preventing violent reactions.
• Limitations: Only suitable for metal fires — dangerous if misused on ordinary Class A, B, or electrical fires.
• Common locations: Laboratories, machine shops, metalworking plants, chemical factories.

Wet chemical fire extinguishers

Wet chemical fire extinguishers spray potassium salts as a fine mist, triggering saponification, meaning the content reacts with burning oils and fats to form a thick, soapy layer.

• Contents: Potassium acetate or potassium citrate solution.
• Colour: Yellow body, label or band.
• Applications: Designed specifically for Class F fires (cooking oils and fats in deep-fat fryers). Can also work on some Class A fires.
• Fire triangle focus: Heat & oxygen – The agent reacts with hot oil, producing a soapy layer that cools and seals the surface, preventing re-ignition.
• Limitations: Not effective on most other fire classes.
• Common locations: Commercial kitchens, restaurants, catering facilities.

Carbon dioxide (CO2) fire extinguishers

Carbon dioxide fire extinguishers take a novel approach to depriving fires of oxygen. Instead of physically shielding the fire from oxygen, they emit a cloud of CO2 that envelops the target, forcing oxygen particles out and away from the blaze.

They’re particularly useful for fighting electrical fires, as the gas particles are so small that they can pass through tiny gaps into electrical equipment, smothering closer to the root.

• Contents: Compressed liquid CO2.
• Colour: Black body, label or band.
• Applications: Best for Class B fires and electrical fires.
• Fire triangle focus: Oxygen – Displaces oxygen around the fire, suffocating the flames, while leaving no residue (safe for electrical equipment).
• Limitations: Ineffective outdoors; risk of frost burns.
• Common locations: Server rooms, offices, workshops.

Clean agent fire extinguishers

Clean agent fire extinguishers are called so because they dispense inert liquids or gases, meaning the contents of these extinguishers do not react with other substances under normal conditions.

Whether liquid- or gas-based, it will be non-conductive and non-volatile.

Unlike the other fire extinguisher types, clean agent fire extinguishers are designed to interrupt the chemical reaction at the core of the fire, rather than focusing exclusively on removing one or more of the fire triangle elements.

• Contents: Halon replacements such as FM-200 or Novec 1230 (environmentally safer than old halon).
• Colour: Green body, label or band.
• Applications: Safe on Class B and electrical fires, sometimes rated for Class C depending on agent.
• Fire tetrahedron focus: Chemical reaction & oxygen – Extinguishes by interrupting the chemical reaction and displacing oxygen, without leaving residue.
• Limitations: Expensive, mainly used where equipment must not be damaged.
• Common locations: Data centres, museums, aircraft, and marine vessels.

How to choose the right fire extinguisher for your workplace

Selecting the appropriate fire extinguisher relies on a clear understanding of the fire risks present in a work environment.

First, you should assess the potential occurrence of each fire class in an area. From there, it’s simply a matter of matching the fire extinguisher to the fire risk.

Use the below table as a quick guide:

 

Only in very rare circumstances will a business require the presence of all the main types of fire extinguisher, but you may well need more than one type depending on the nature of the work, equipment, and materials at play.

A commercial kitchen, for example, will likely require a wet chemical fire extinguisher in case of Class F fires, which involve oils and fats, and some form of fire extinguisher suitable for fighting electrical fires due to all the appliances in daily use.

Where should a workplace fire extinguisher be kept?

Workplace fire extinguishers should be clearly visible and easily accessible, in close proximity (but not too close) to where the fire may realistically ignite.

They’re commonly mounted on walls or in cabinets, making them accessible without getting in the way of daily operations. However, the mount height is of utmost importance. They need to be reached quickly and with minimal strain.

If possible, there should be a clear route from the potential fire hazard to the fire extinguisher, ensuring workers can retrieve the extinguisher and return to the breakout as efficiently as possible.

Who needs to know about fire extinguishers in the workplace?

Anyone who will be working near or with potential fire risks needs to know where your workplace fire extinguishers are kept, what type of fire extinguishers they are, and how to use them.

This includes all employees, contractors, and even visitors in certain environments. Proper training ensures that in the event of a fire, staff can respond quickly and safely, minimising damage, preventing panic, and potentially saving lives.

Employers are responsible for making sure that fire extinguisher information is clearly communicated, equipment is maintained, and refresher training is provided regularly.

Download our whitepaper on managing fire safety in commercial and residential premises.

As part of our eLearning suite, we offer both Fire Safety and Fire Marshal training for employers and employees.

Fire Safety covers the essential basics of fire prevention and suppression – ideal for all personnel working around potential fire hazards. Learn more about our Fire Safety course.

Our Fire Marshal course is designed for your specified fire warden, ensuring they can effectively support fire safety management and emergency evacuation procedures in the workplace. Get the details on our Fire Marshal eLearning course.

How to use a fire extinguisher – step-by-step guide

You should only attempt to use an extinguisher if the fire is small, you have a clear escape route behind you, the alarm has been raised (or someone is calling emergency services), and it’s safe to do so. If in doubt, evacuate and let the fire service handle it.

If these factors are accounted for, here’s how to use a fire extinguisher:

Step 1. Preparation

1. Check the extinguisher is appropriate for the type of fire. This is particularly important for areas with more than one fire extinguisher and hazards spanning multiple fire classes.

2. Position yourself with your back to the nearest safe exit so you can retreat quickly.

Step 2. Follow the P.A.S.S sequence

1. Pull the pin – which breaks the tamper seal and allows the handle to be depressed.

2. Aim low, pointing the nozzle at the base of the fire rather than the flames. Start from a safe distance, between 1 and 3 meters away depending on the size and ferocity of the fire.

3. Squeeze the handle to release the extinguishing agent. It’s best to use controlled bursts rather than long, uninterupted depressions.

4. Sweep from side to side, moving the nozzle across the base of the fire, gradually moving closer as the flames die back. Continue until the fire appears to have gone out.

While extinguishing:

• Never turn your back on the fire.
• If the fire extinguisher runs out and the fire is still burning, leave immediately.
• If you’re clothes catch fire – stop, drop and roll, then evacuate ASAP.

Once the fire is extinguished:

• Watch for re-ignition. If the fire returns, stop fighting it and evacuate.
• If the fire remains extinguished, have the area checked by the fire service.
• Report the incident to your supervisor and arrange replacements/recharging of the fire extinguisher used to fight the fire.
• Record valuable information about the event, including the date, location, cause, procedure followed, lessons learned, and training required to improve response during future fire emergencies.

Fire extinguisher maintenance requirements in the workplace

Fire extinguishers are a critical part of your workplace fire safety equipment. Because they are pressurised and must work immediately in an emergency, regular checks and servicing are essential. Poorly maintained extinguishers can fail when you need them most.

Routine fire extinguisher checks involve a monthly visual inspection (by a competent person on site):

• Ensure extinguishers are in their correct location and easily accessible.
• Check the pressure gauge (needle must be in the green zone).
• Confirm safety pin and tamper seal are intact.
• Look for obvious damage, corrosion, or leakage.
• Check instructions on the label are legible.
• Make sure the operating hose/nozzle is not blocked or cracked.
• Record findings in your fire safety logbook for accountability and compliance.

Annual fire extinguisher servicing:

• A basic service should be carried out every 12 months by a qualified fire safety technician.
• The technician will check weight, pressure, seals, and general condition, and confirm the extinguisher meets safety standards.

Extended fire extinguisher servicing/overhaul:

Depending on the extinguisher type:

• Water, foam, dry powder, wet chemical, clean agent — every 5 years.
• CO₂ extinguishers — every 10 years.

These services may involve a discharge test, internal inspection, recharging, and replacement of key components.

Fire extinguisher replacement:

• Extinguishers that fail inspection or servicing must be removed from service immediately.
• Replace extinguishers that are more than 20 years old, heavily corroded, or repeatedly failing checks.

Fire Risk Services from Cardinus

At Cardinus, we understand that the right fire safety measures go far beyond simply having extinguishers in place.

As part of our property services, we provide comprehensive fire risk solutions, including:

• Destructive fire risk assessments
• Non-destructive fire risk assessments
• Fire safety consultancy
• External wall systems review and certification
• Remedial work
• Consultancy lead on technical fire safety projects

We can evaluate any property type, anywhere in the UK. And, if required, we can carry out a Reinstatment Cost Assessment during the same visit, giving you peace of mind that fire and underinsurance risks are controlled.

To support your workforce directly, we also offer fire safety eLearning courses, designed to reach at-risk workers quickly and effectively with essential training. These courses make it simple for employers to build awareness, meet regulatory requirements, and keep staff safe.

Contact Cardinus today to find out how our fire risk services and training solutions can help protect your business.