Fire Safety Glossary

A 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.

A 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.

A fire blanket is a sheet of fire-resistant material — typically woven fibreglass — used to smother small Class F fires involving burning cooking oils and fats, or to wrap around a person whose clothing is on fire. Required in commercial kitchens alongside a wet chemical extinguisher, fire blankets must meet BS EN 1869:2019 and must be replaced after any use — they are single-use devices.

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.

A 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.

A 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.

A 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.