There are five main fire extinguisher types in the UK: water (red), foam (cream), dry powder (blue), CO2 (black) and wet chemical (yellow). Since 1997 every extinguisher body has been predominantly red under BS EN 3, with a coloured band or panel identifying the contents. Using the wrong one can make a fire worse — water on a live electrical fire or on burning cooking oil is genuinely dangerous.
This guide covers each type, the fire classes they are rated for, the ones you should never use on electrical equipment, and what UK law actually requires you to provide.
What are the classes of fire?
Extinguishers are rated against fire classes, so the classes come first. The British and European standard classification used in the UK is:
| Class | What is burning |
|---|---|
| Class A | Solids — wood, paper, cardboard, textiles, most plastics |
| Class B | Flammable liquids — petrol, diesel, oils, paints, solvents |
| Class C | Flammable gases — butane, propane, methane |
| Class D | Metals — magnesium, lithium, aluminium swarf |
| Class F | Cooking oils and fats — deep fat fryers |
You will often see “Class E” used for electrical fires. It is not an official class. Electricity is a source of ignition rather than a fuel, so extinguishers are instead marked as safe or unsafe for use near live electrical equipment, usually with a dielectric test rating such as 35 kV.
Water extinguishers (red label)
Class A only. Water cools the fuel below its ignition temperature. It is the cheapest option and works well on paper, wood and textiles, which is why it suits offices, schools, shops and warehouses.
Never use water on: live electrical equipment, burning liquids, or cooking oil. Water conducts electricity, and poured onto burning oil it flashes to steam instantly and ejects burning fat — the cause of a great many serious kitchen injuries.
Foam extinguishers (cream label)
Classes A and B. Foam — usually AFFF — both cools and forms a blanket that seals the vapour off from the air. That makes it the most common general-purpose extinguisher in UK premises with any flammable liquid present, such as garages, workshops and plant rooms.
Most foam extinguishers are dielectrically tested and so are safer than water near electrical equipment, but they are still not rated for electrical fires. Treat them as a water-based extinguisher and isolate the supply first.
Dry powder extinguishers (blue label)
Classes A, B and C, and safe on live electrical equipment. Powder interrupts the chemical reaction of combustion. It is the only common type rated for flammable gases, and specialist M28 or L2 powders handle Class D metal fires.
The breadth is tempting, but powder has real drawbacks indoors. It creates a dense cloud that destroys visibility just when people are trying to escape, it is an inhalation risk, and it causes severe damage to electronics and machinery. Standard guidance is not to install dry powder extinguishers in occupied indoor spaces — they are for outdoor and vehicle use, forecourts, plant and boiler rooms.
CO2 extinguishers (black label)
Class B and safe on live electrical equipment. Carbon dioxide displaces oxygen and leaves no residue, which is why it sits beside server rooms, switch rooms, laboratories and office electrics.
Two cautions. The horn becomes extremely cold in use — modern extinguishers have frost-free horns, older ones cause cold burns if held wrongly. And because CO2 displaces oxygen, discharging one in a small unventilated room is an asphyxiation risk. CO2 also has almost no cooling effect, so deep-seated Class A materials can reignite once the gas disperses.
Wet chemical extinguishers (yellow label)
Class F, and usually Class A. A fine mist of potassium salts reacts with hot cooking oil in a process called saponification, forming a soapy crust that seals the surface and cools it below ignition point.
If you run a commercial kitchen with a deep fat fryer, this is the extinguisher you need. Nothing else on this list deals with burning cooking oil safely.
Which extinguisher for an electrical fire?
CO2 or dry powder — and given powder’s problems indoors, CO2 in practice for offices and server rooms. But the first action is to isolate the supply if it is safe to do so. Once the power is off, the fire becomes a fire of whatever the equipment is made from, usually Class A.
Does the law say how many extinguishers I need?
The Regulatory Reform (Fire Safety) Order 2005 requires the responsible person to equip premises with appropriate firefighting equipment, but it does not state a number. The quantity, type and siting come from your fire risk assessment, informed by the British Standard BS 5306.
The commonly applied benchmarks are a minimum of two Class A extinguishers per floor, extinguishers sited on escape routes and near exits, and a maximum travel distance of about 30 metres to reach one. Extinguishers must be maintained — a basic annual service by a competent person, with an extended service or replacement at longer intervals depending on type.
Should staff actually fight a fire?
Only if they have been trained, the fire is small and not spreading, they have a clear escape route behind them, and the alarm has been raised. Nobody should ever be expected to tackle a fire. Evacuation is always the priority, and a first-aid firefighting attempt should be abandoned the moment it does not work immediately.
Related guides
- Fire safety training: what UK law requires and what it does not
- Fire risk assessment: the 5 steps explained
Fire extinguisher training
Our Fire Extinguisher Awareness course covers the classes of fire, each extinguisher type and its colour code, when tackling a fire is and is not appropriate, and the PASS technique. £9 per course. CPD accredited, 100% online, verifiable e-certificate. Pay for 2, get 3 — any 3 courses for £18.
General information, not legal advice. Extinguisher selection, quantity and siting must follow your own fire risk assessment and the relevant British Standard. This article covers England and Wales; requirements differ in Scotland and Northern Ireland. Nexis CPD courses are CPD-accredited awareness training, not Ofqual-regulated qualifications, and awareness training is not a substitute for hands-on practical extinguisher training where your risk assessment calls for it.