Food Hygiene
Health & Safety
Safeguarding
First Aid
Business Skills
Personal Development
Not every fire extinguisher can be used on every fire — and using the wrong one can make things worse, not better. Water on an electrical fire, for example, can cause electrocution. Foam on a chip-pan fire can cause a flare-up.
To choose the right extinguisher, you first need to understand two things: fire classes (what’s burning) and extinguisher types (what puts it out). This guide covers both, plus the colour-coding system, how to use an extinguisher safely, and what UK law requires.
The 6 Classes of Fire in the UK
Fires are classified by British and European Standard BS EN 2 according to the fuel that’s burning. There are five formally defined classes (A–F, skipping E) — plus electrical fires, which are treated as a distinct risk category in practice even though they aren’t a formal BS EN 2 class.
Why isn’t there a Class E? Electrical fires aren’t given a formal letter under BS EN 2 because, technically, the fire itself is fuelled by whatever catches alight near the electrical equipment (usually plastic casing or insulation — Class A material). The “electrical” label is really a safety instruction: don’t use a conductive extinguishing agent near live current. Once the power is isolated, an electrical fire behaves like whatever class of fire it becomes.
The 8 Types of Fire Extinguishers and What They're For
There are eight recognised fire extinguisher types in the UK, though most premises only need two or three.
| Type | Fire Classes | Best For | Avoid On |
|---|---|---|---|
| Water (jet/spray) | A | Offices, schools, warehouses | Electrical, liquid, oil fires |
| Water mist | A, F, and electrical (if dielectrically tested) | Mixed-risk sites, care homes, hospitals | Check manufacturer rating before use on live electrics |
| Foam | A, B | Garages, workshops, petrol stations | Unrated electrical equipment |
| Standard dry powder (ABC) | A, B, C | Vehicles, industrial sites, outdoor areas | Enclosed spaces (reduces visibility, hard to clean up) |
| Specialist dry powder | D | Workshops handling reactive metals (magnesium, lithium) | General-purpose use |
| CO₂ | B and electrical | Server rooms, offices with electrical equipment | Poorly ventilated confined spaces; limited effect on Class A |
| Wet chemical | F (and A) | Commercial kitchens, restaurants | Anywhere without a cooking-oil risk |
| Clean agent (gaseous) | B, C, and electrical | Server rooms, archives, museums — anywhere residue would cause damage | Cost-sensitive, low-risk environments (expensive) |
Water fire extinguishers
The most common extinguisher type, used on Class A fires only. Water cools the fuel below its ignition point. Never use on electrical fires (conduction risk) or burning liquids/fats (can spread the fire).
Water mist extinguishers
A newer technology using de-ionised water released as a fine mist. Because the water droplets are non-conductive at a safe distance, some water mist extinguishers are dielectrically tested for use near live electrical equipment up to 1000V — always check the rating on the specific unit before relying on this. Effective on Class A and, with the right rating, Class F fires too, making them a flexible single-unit option for mixed-risk premises.
Foam fire extinguishers
Cover Class A and B fires. The foam forms a film over burning liquid, cutting off oxygen and vapour while cooling the fuel. A common choice for premises with both paper/furniture risk and small liquid risks (cleaning solvents, forklift fuel).
Dry powder fire extinguishers (standard vs specialist)
Standard (ABC) dry powder tackles Class A, B and C fires by interrupting the fire’s chemical reaction. Versatile, but not recommended indoors — the powder reduces visibility and is difficult to clean up, and inhaling it isn’t pleasant.
Specialist dry powder is a different, more targeted formulation for Class D metal fires. Standard powder is not effective on burning metals — this is a common and dangerous mix-up.
CO₂ fire extinguishers
Designed for electrical fires and Class B liquid fires. CO₂ displaces oxygen and cools the fire without leaving a residue, which is why it’s the standard choice for server rooms and offices full of electrical kit. Limited effectiveness on Class A fires, and should be used with care in small, unventilated spaces.
Wet chemical fire extinguishers
Purpose-built for Class F cooking oil and fat fires. The agent cools the fire and forms a soap-like layer over the surface, preventing re-ignition — far more effective on deep-fat-fryer fires than water or foam, both of which can cause a dangerous flare-up.
Clean agent (gaseous) extinguishers
Use an inert gas or chemical agent that leaves no residue on evaporation, making them suitable for server rooms, archives, and anywhere water or powder would cause more damage than the fire itself. Effective on B, C and electrical fires. Higher cost limits their use to specific high-value environments.
Fire Extinguisher Colour Codes
Since 1997, all fire extinguishers sold in the UK have red bodies (known as “signal red”) to comply with BS EN 3. The type of extinguisher is shown by a coloured band or panel near the top of the cylinder, not the body colour.
| Colour Band | Extinguisher Type | Fire Classes |
|---|---|---|
| Red (no band — solid red) | Water | A |
| Cream | Foam | A, B |
| Blue | Dry powder | A, B, C (and D for specialist) |
| Black | CO₂ | B, electrical |
| Yellow | Wet chemical | F |
Water mist and clean agent extinguishers don’t have a single standardised band colour under BS EN 3 in the way the five main types do — always check the label rather than relying on colour alone for these two.
Note: older extinguishers manufactured before 1997 may still be found with fully coloured bodies (all-red, all-blue, etc.). These remain legal to use if properly serviced, with one exception: green-bodied halon extinguishers, which were banned for general use in 2003 under the Montreal Protocol. If you find one, arrange disposal through a licensed halon disposal service or your local fire service — don’t just bin it.
Understanding Extinguisher Ratings (13A, 55B, etc.)
Every extinguisher is marked with a rating like 13A or 55B. This isn’t a size in litres or kg — it indicates the size of test fire the extinguisher can put out under controlled conditions. A higher number means greater firefighting capacity, so a 13A-rated water extinguisher can handle a larger Class A test fire than a 5A-rated one of the same type. Use the rating, not just the physical size of the unit, when comparing extinguishers for a given risk level.
How to Choose the Right Fire Extinguisher
Match the extinguisher to the actual risks in the space, not just the industry:
- Offices: Water or water mist for general Class A risk, plus CO₂ near server rooms/electrical equipment
- Kitchens (commercial): Wet chemical, in addition to whatever covers the rest of the building
- Industrial/workshop sites: Dry powder (standard), with specialist dry powder if reactive metals are present
- Garages, forecourts, workshops: Foam
- Mixed-risk or open-plan sites: A combination, informed by a proper risk assessment
Comparison at a Glance
| Type | Classes Covered | Typical Cost (Small Unit) | Environment |
|---|---|---|---|
| Water | A | £25–£45 | Offices, schools |
| Water mist | A, F, some electrical | £45–£90 | Care homes, mixed-risk sites |
| Foam | A, B | £30–£55 | Garages, workshops |
| Dry powder (standard) | A, B, C | £30–£85 | Industrial, vehicles, outdoor |
| Dry powder (specialist) | D | £60–£120 | Metal workshops |
| CO₂ | B, electrical | £35–£90 | Server rooms, offices |
| Wet chemical | F | £45–£80 | Commercial kitchens |
| Clean agent | B, C, electrical | £150–£500+ | Server rooms, archives |
Prices are indicative for small commercial units and will vary by supplier and size — always get a current quote before budgeting.
How to Use a Fire Extinguisher: The PASS Technique
Only ever attempt to fight a fire if it’s small and contained, everyone else has evacuated, the fire brigade has been called, and you have a clear escape route at your back. Otherwise, leave immediately.
- P — Pull the safety pin to break the tamper seal.
- A — Aim the nozzle or hose at the base of the fire, not the flames themselves, from roughly 2 metres away.
- S — Squeeze the handle slowly and evenly, keeping the extinguisher upright.
- S — Sweep side to side across the base of the fire until it’s fully out or the extinguisher is empty.
If the fire doesn’t go out quickly, or the room starts filling with smoke, stop and evacuate. No fire extinguisher is a substitute for calling the fire brigade.
How Many Fire Extinguishers Do You Need — and Where?
UK guidance (BS 5306-8) generally recommends:
- At least two Class A-rated extinguishers per floor in most workplaces
- No one should have to travel more than 30 metres to reach an extinguisher
- Extinguishers positioned near exits and escape routes, not tucked away in corners, so they can be grabbed on the way out and used with an exit at your back
- Wall-mounted on brackets at a consistent height, with clear signage even when visibility is reduced by smoke
The exact number and type depend on your fire risk assessment — floor area, occupancy, and specific hazards (kitchens, server rooms, workshops) all affect requirements.
UK Legal Requirements
Under the Regulatory Reform (Fire Safety) Order 2005, the “responsible person” for a workplace (usually the employer, building owner, or occupier) must:
- Carry out and regularly review a fire risk assessment
- Provide appropriate fire-fighting equipment, including extinguishers matched to the identified risks
- Ensure equipment is serviced and maintained in line with BS 5306-3
- Keep extinguishers accessible and clearly signed
Servicing: extinguishers should have a visual check monthly (by staff) and a full service by a competent engineer annually. Depending on type, extinguishers also need an extended/discharge service every 5 years and are typically retired after 10–12 years, though CO₂ and some pressurised types have shorter intervals — check manufacturer guidance for your specific units.
Frequently Asked Questions (FAQ)
What are the 5 main types of fire extinguishers?
Water, foam, CO₂, dry powder, and wet chemical are the five most common types. Water mist and clean agent are newer additions, and specialist dry powder is a distinct sub-type for metal fires — bringing the total to eight recognised types in the UK.
Can I use one fire extinguisher for all fire types?
No. There is no single extinguisher rated for every fire class. Using the wrong type can make a fire worse — for example, water conducts electricity and can cause a fat fire to flare up dangerously.
Do I need a fire extinguisher at home?
It’s not a legal requirement for most homes, but it’s strongly recommended, particularly a multi-purpose extinguisher for the kitchen and living areas.
How long do fire extinguishers last?
Most extinguishers have a service life of 10–12 years, with CO₂ and wet chemical types often serviced on a 5-year cycle. They should be replaced or professionally recharged rather than used past their service interval.
What's the difference between Class C fires and electrical fires?
Class C refers to burning gases (propane, butane, methane). “Electrical fire” is a safety category, not a formal fire class — it describes any fire involving live electrical equipment, where using a conductive agent like water creates an electrocution risk.
Can you use a CO₂ extinguisher on a chip-pan fire?
No. Use a wet chemical extinguisher, or smother the pan with a fire blanket after turning off the heat if safe to do so. CO₂ isn’t designed for Class F cooking oil fires.
