Fire Extinguisher Buyers Guide

Choosing the right fire extinguisher comes down to one question: what type of fire is most likely in your environment? Get that right and everything else follows. This guide covers all six extinguisher types used across UK workplaces — water, foam, CO2, dry powder, wet chemical, and lithium battery — with clear advice on which to choose, what size you need, and what the law requires.

1. Fire Classes: Start Here

UK fire safety uses a letter classification system (defined in BS EN 2) to match extinguisher types to fire risks. Most buildings carry more than one risk — an office with a kitchen may have Class A materials, Class F cooking risks, and electrical equipment requiring CO2 coverage, which is why pairing extinguisher types is standard practice.

• Class A — Solid combustibles: wood, paper, textiles, cardboard, plastics
• Class B — Flammable liquids: petrol, solvents, paints, oils (not cooking fat)
• Class C — Flammable gases: LPG, propane, butane, methane, acetylene
• Class D — Combustible metals: titanium, magnesium (specialist industrial environments only)
• Class F — Cooking oils and fats: deep fat fryers, commercial catering equipment
• Electrical fires — Not assigned a class letter in UK/BS EN3. Use CO2 or dry powder; never water or foam on live electrical equipment.

2. Which Type of Extinguisher Do You Need?

Water Extinguishers — Class A

Water extinguishers cool the fire, removing the heat needed to sustain combustion. Suitable for wood, paper, textiles, and most solid combustible materials. Never use on electrical fires or flammable liquids — water conducts electricity and will spread a liquid fire. Identified by a red label with no colour band. The 6L spray variant is suitable for environments with incidental electrical risk, as the spray pattern reduces conductivity. Best suited to warehouses, stockrooms, and retail premises with large quantities of Class A materials.

Foam Extinguishers — Class A & B

Foam extinguishers are the most versatile general-purpose option, covering both Class A and Class B fires. The foam smothers the fire and creates a seal that prevents re-ignition — particularly effective for petrol and solvent fires. Identified by a cream label. Available in 6L, 2L spray, and 9L. The go-to choice for most commercial premises, workshops, and warehouses where flammable liquids are stored alongside general combustibles.

CO2 Extinguishers — Electrical risks & Class B

CO2 extinguishers displace oxygen to suffocate the fire without leaving any residue — the correct choice for server rooms, offices with electrical equipment, and environments where contamination from powder or foam would cause secondary damage. Identified by a black label. Available in 2kg and 5kg. Note: CO2 does not cool the fire source, so there is a risk of re-ignition if the heat source remains — always isolate the power supply.

Dry Powder Extinguishers — Class A, B & C

ABC dry powder extinguishers interrupt the chemical chain reaction of the fire and offer the broadest coverage of any type — effective against Class A, B, and C (flammable gas) fires. Identified by a blue label. Available in 1kg and 2kg. Important caveat: powder leaves a fine residue that contaminates food preparation areas and damages sensitive electronics. Not suitable for offices, kitchens, or server rooms. Best used in external environments, plant rooms, construction sites, and vehicles.

Wet Chemical Extinguishers — Class F

Wet chemical extinguishers are the only type approved for Class F fires — cooking oils and fats that have reached extreme temperatures well above their flashpoint. The wet chemical agent reacts with the burning fat through saponification, forming a soapy foam layer that seals the surface and prevents re-ignition. Identified by a yellow label. A legal requirement for any commercial kitchen operating a deep fat fryer. Never use water, foam, CO2, or powder on a fat fire — the result is a violent explosive reaction that will spread burning oil across the room.

Lithium Battery Extinguishers — Li-ion thermal runaway

Lithium-ion battery fires involve thermal runaway — extreme temperatures that can persist and cause re-ignition long after a fire appears out. Standard extinguishers cannot adequately suppress this. Firechief lithium battery extinguishers use a specialist agent that rapidly cools the battery cells to prevent re-ignition. Available in 2L and 6L. The correct choice for EV charging points, e-bike storage, warehouses handling consumer electronics, and any location where lithium-ion batteries are charged or stored in volume.

3. What Size Do You Need?

For most commercial premises, BS 5306-8 and the Regulatory Reform (Fire Safety) Order 2005 require a minimum of two Class A extinguishers per floor. Practical guidance by environment:

• Small office (under 100m²): 2 × 6L foam; add a 2kg CO2 for electrical equipment
• Open-plan office or retail (100–500m²): 2 × 9L foam + 1 × 5kg CO2 per floor
• Warehouse or industrial unit: 9L water or foam at each fire exit; CO2 near electrical panels
• Server room or data centre: 5kg CO2 only — no powder, no foam
• Vehicle: 1kg or 2kg ABC powder (compact and multi-purpose)
• Commercial kitchen: Class F wet chemical for cooking fat + CO2 for electrical equipment

If you're unsure of the requirement for your premises, your fire risk assessment — a legal requirement for all non-domestic premises — should specify both type and quantity.

4. UK Legal Requirements

Under the Regulatory Reform (Fire Safety) Order 2005, all non-domestic premises in England and Wales must carry out a fire risk assessment and provide appropriate fire-fighting equipment — the right types, in the right quantities, in the right locations. Fire extinguishers for UK commercial use must meet BS EN 3 and carry a Kitemark or equivalent conformity mark. All Cocus fire extinguishers meet this standard.

Annual servicing by a competent person is a legal requirement for commercial premises. Monthly visual checks — pressure gauge in the green zone, pin and tamper seal intact, label legible — are recommended as a minimum between annual services.

5. Mounting and Accessories

An extinguisher stored on the floor or in a cupboard is inaccessible in an emergency. Correct mounting at approximately 1m handle height ensures it can be reached and operated quickly. Cocus stocks a range of stands and mounts, including single stands and double stands for locations without a wall mounting point.

Frequently Asked Questions

Can I use any extinguisher on an electrical fire?
No. Only CO2 and dry powder are safe to use on live electrical equipment. Water and foam conduct electricity — using them on an electrical fire risks electrocution and will spread the fire. Always use CO2 where possible, as it leaves no residue.

How long does a fire extinguisher last?
Most extinguishers have a working life of 5–10 years. CO2 cylinders require hydrostatic testing every 10 years. Regardless of age, any extinguisher that has been discharged — even partially — must be replaced or recharged before being returned to service.

How many extinguishers do I need?
BS 5306-8 recommends one extinguisher unit per 200m² of floor area, with a minimum of two per floor. The exact number depends on your fire risk assessment. Higher-risk environments — flammable liquids storage, large electrical installations — require additional coverage.

Is it safe to buy second-hand fire extinguishers?
No. There is no reliable way to verify the service history, discharge history, or internal condition of a used extinguisher. Always purchase new from a reputable UK supplier and ensure the extinguisher carries a current service label and BS EN 3 conformity mark.

Do you sell stands and accessories?
Yes — Cocus stocks a full range of extinguisher stands, wall brackets, and covers compatible with all sizes in our range.

Browse the full Cocus fire extinguisher range — water, foam, CO2, dry powder, wet chemical, and lithium battery types, all meeting BS EN 3, available with next-day delivery across the UK.