Definition
Fire Classes
Fire classes are the European classification system — Class A (solid combustibles), Class B (flammable liquids), Class C (flammable gases), Class D (combustible metals), and Class F (cooking oils and fats) — used to categorise fires by fuel type. Selecting the correct fire extinguisher requires matching the extinguishing agent to the fire class present in the premises, as specified in BS 5306-8.
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View training courseUnderstanding UK Fire Classes
Every portable fire extinguisher is designed to tackle specific types of fire. Using the wrong extinguisher — such as water on a flammable liquid fire, or water on live electrical equipment — can cause the fire to spread or create an electrocution hazard. The European fire class system provides a standardised framework for categorising fires by the type of material burning, making it straightforward to match the correct extinguishing agent to the risk.
The Fire Classes Explained
- Class A — Fires involving solid, organic combustibles that form a glowing ember on burning. Materials include wood, paper, cardboard, textiles, rubber, and many plastics. Water, foam, and ABC powder extinguishers are effective. The most common class in offices and residential premises.
- Class B — Fires involving flammable liquids or liquefiable solids, including petrol, diesel, oils (excluding cooking oils), paint, solvents, and wax. Foam or CO2 extinguishers should be used. Never use water — it can cause burning liquid to scatter.
- Class C — Fires involving flammable gases such as propane, butane, methane, and hydrogen. The correct approach is to shut off the gas supply rather than extinguish the flame; extinguishing without isolating the source risks an explosion from unburned gas.
- Class D — Fires involving combustible metals such as magnesium, titanium, lithium, sodium, and potassium. These require specialist dry powder extinguishers formulated for the specific metal. Standard extinguishers should never be used on Class D fires.
- Class F — Fires involving cooking oils and fats at high temperature, such as in deep fat fryers and chip pans. These are among the most dangerous fire types — burning oil can reach over 360 °C, well above its autoignition temperature. A wet chemical extinguisher is the only suitable agent; never use water.
What About Electrical Fires?
"Electrical fire" is not an official fire class — it describes a fire in which live electrical equipment is involved or adjacent. The underlying fire is usually Class A or B. The concern is the risk of electrocution to the user. CO2 and dry powder extinguishers are non-conductive and safe to use near live electrical equipment up to 1,000 V (CO2) or 1,000 V (dry powder) according to BS EN 3. Water and foam must never be used on live electrical equipment.
Matching Extinguishers to Fire Classes
Under BS 5306-8, fire extinguishers must be selected to cover the fire risks present in the premises. In most offices and commercial buildings, a combination of water or foam extinguishers (for Class A) and CO2 extinguishers (for electrical risks) is the standard provision. Commercial kitchens require a wet chemical extinguisher for Class F risk alongside CO2 for electrical equipment.
The number and rating of extinguishers required depends on the floor area and risk category of the premises — a risk assessment and selection exercise by a competent person, qualified to the BFC EAL Level 3 Fire Extinguisher standard, ensures the correct provision.
Related Terms
- CO2 Fire ExtinguisherFire ExtinguishersA CO2 (carbon dioxide) fire extinguisher is a portable firefighting device that discharges pressurised carbon dioxide gas to smother a fire by displacing oxygen. It leaves no residue, making it the preferred choice for electrical equipment, server rooms, and environments where contamination cannot be tolerated.View definition
- Water Fire ExtinguisherFire ExtinguishersA water fire extinguisher is a portable firefighting device that discharges pressurised water to cool burning materials and prevent re-ignition. Identified by a red label panel, it is effective on Class A fires — solid combustibles such as wood, paper, and textiles — but must never be used on electrical fires, flammable liquids, or cooking oils. Annual servicing is required under BS 5306-3.View definition
- Foam Fire ExtinguisherFire ExtinguishersA foam fire extinguisher is a portable firefighting device that discharges AFFF (aqueous film-forming foam) to smother fires by forming a vapour-suppressing barrier and cooling the burning material. Effective on Class A (solid combustibles) and Class B (flammable liquids) fires, it is identified by a cream label panel and must be serviced annually under BS 5306-3.View definition
- Wet Chemical Fire ExtinguisherFire ExtinguishersA wet chemical fire extinguisher is specifically designed for Class F fires involving burning cooking oils and fats. It discharges a fine mist of alkaline potassium solution that reacts with hot oil through saponification — forming a cooling, vapour-suppressing foam — and preventing dangerous re-ignition. Identified by a yellow label panel, it must be serviced annually under BS 5306-3.View definition
- Dry Powder Fire ExtinguisherFire ExtinguishersA dry powder fire extinguisher discharges a fine chemical powder — typically mono-ammonium phosphate — to interrupt the combustion chain reaction. Effective on Class A, B, and C fires and live electrical equipment, it is identified by a blue label panel. Powder causes significant contamination and poor visibility, so its use in occupied buildings should be a last resort, per BS 5306-8.View definition
Frequently Asked Questions
Fire classes are the European classification system — Class A (solid combustibles), Class B (flammable liquids), Class C (flammable gases), Class D (combustible metals), and Class F (cooking oils and fats) — used to categorise fires by fuel type. Selecting the correct fire extinguisher requires matching the extinguishing agent to the fire class present in the premises, as specified in BS 5306-8.
Requirements for fire classes in the UK depend on the type of premises and applicable legislation, including the Regulatory Reform (Fire Safety) Order 2005 and relevant British Standards. The responsible person for a premises must ensure adequate fire safety provisions are in place. The British Fire Consortium can provide guidance — contact our team or search our member directory to find a qualified specialist.
Fire Classes and CO2 Fire Extinguisher are related fire safety concepts but serve different purposes. See our individual glossary entries for detailed definitions. For expert guidance on which applies to your premises, consult a BFC member company.
The British Fire Consortium offers EAL Level 3 accredited training covering fire safety systems including topics related to fire classes. Our courses are the only nationally recognised Level 3 qualifications across all fire disciplines. View our training courses or use the member directory to find a qualified trainer near you.