Fire Extinguisher Types: Which One Fights Which Fire, and What Your Premises Needs
By the DC Fire & Security engineering team — installing and maintaining fire and security systems since 2010. Updated July 2026.
Quick answer
There are six extinguisher types in UK use: water (ordinary solids), water mist (the flexible newcomer — most solid and liquid fires, many rated for electrical), foam (solids plus flammable liquids), dry powder (the outdoor generalist — solids, liquids, gases, electrical, but a nightmare indoors), CO2 (electrical equipment and liquids, no residue), and wet chemical (the only proper answer to cooking-oil fires). Most workplaces need just two of them: the classic pairing is foam (or water) plus CO2 on every floor, with wet chemical added in kitchens and powder where vehicles or gases live.
The six types against the six fire classes
| Type | Fire classes | Strengths | Never use on |
|---|---|---|---|
| Water | A (wood, paper, textiles) | Cheap, effective soak on solids, no chemical residue | Electrical, flammable liquids, cooking oil |
| Water mist | A, some B and F ratings; many models tested for live electrical to 1,000V | One-cylinder-covers-most flexibility, minimal damage, no chemicals | Check the label per model — ratings vary more than any other type |
| Foam (AFFF) | A and B (petrol, solvents, paints) | Smothers liquid fires, re-ignition barrier | Cooking oil; treat electrical as off-limits unless dielectrically tested |
| Dry powder (ABC) | A, B, C (gases); safe on electrical | The broadest coverage and the choice outdoors, on vehicles, LPG, plant | Enclosed spaces if avoidable — visibility loss, inhalation, wrecks electronics; never fryers |
| CO2 | B and electrical | Zero residue — the server-room and office standard alongside foam | Class A solids (re-ignites), confined spaces; never grip the horn |
| Wet chemical | F (cooking oils/fats) and A | The only type designed for deep-fat fryer fires — cools and seals the oil | Class B liquids, electrical unless label states otherwise |
Ratings: what 13A and 55B on the label mean
Every extinguisher carries a fire rating — 13A, 21A, 55B, 75F — which is the size of test fire it extinguished in certification. The number scales with capability, the letter is the fire class: a 21A water unit kills a bigger wood-crib fire than a 13A; a 144B foam handles a larger liquid tray than a 55B. This is the number that matters when comparing units — a 'big red extinguisher' with a small rating is theatre.
Ratings are also how provision is calculated. The benchmark from BS 5306-8 works out at a combined 26A per floor as the starting point for ordinary Class A risk (scaled to floor area) — which in practice means two 13A-rated extinguishers per floor as the familiar minimum. Your fire risk assessment does this arithmetic against your actual layout; the extinguisher colours guide covers identifying what's already on your walls.
The standard combinations that cover real premises
- Office floor — foam 13A + CO2 by the exits: solids covered, electricals covered, no residue disasters in the server cupboard
- Commercial kitchen — wet chemical within reach of the fryers + fire blanket + CO2 for the electrics; staff trained that water never enters the equation
- Warehouse / workshop — foam or water for the racking and packaging, CO2 at the charging stations, powder where LPG trucks or vehicles operate
- Construction site — powder's home turf: mixed fuels, outdoors, vehicles and temporary electrics
- Landlord common parts — often minimal or none by design: in many blocks the strategy is evacuation, not amateur firefighting, and the fire risk assessment decides — not the catalogue
- Server / comms rooms — CO2 only; powder in a server room is a total-loss event even for a small fire
Water mist and lithium: the two modern wrinkles
Water mist deserves its growing popularity: de-ionised water as a fine mist, rated across solid fires, many liquid fires and often live electrical to 1,000V, leaving near-zero damage. For mixed-risk premises wanting to simplify to one type on the wall, it's the one to price — with the caveat that ratings vary sharply by model and size, so the label does the deciding, not the category.
Lithium-ion batteries — e-bikes, scooters, power tools — are the fastest-growing fire risk in UK buildings, and none of the six standard types properly extinguishes a battery in thermal runaway. Specialist lithium agents exist and the market is maturing; until it settles, the honest controls are prevention (charging rules, no escape-route charging, storage) and early detection. If your premises has an e-bike habit, your fire risk assessment should already say so.
Servicing is the same regardless of type: annual basic service to BS 5306-3, extended service at five years (ten for CO2), and a service label that proves it — covered in more depth in the colours guide.
Frequently Asked Questions
What are the 5 main types of fire extinguisher?
Which fire extinguisher is used for electrical fires?
What is a 13A fire extinguisher?
Can I use a fire extinguisher on a chip pan fire?
How many fire extinguishers do I need in my business?
Do you sell or service fire extinguishers?
The extinguisher schedule should come from a risk assessment — that's us
We don't sell extinguishers, so there's no upsell in this guide. What we do across Luton, Bedfordshire, Hertfordshire and North London is the compliance around them: fire risk assessments that specify exactly what your premises needs, plus fire alarms, fire doors and fire stopping. If nobody has formally specified your extinguisher cover, start there.
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