system,fire_class,fuel_type_description,suitable_extinguishing_agents,unsuitable_agents,uk_colour_code_bs_en3,us_label_convention_nfpa,governing_standard,notes
US (NFPA),A,"Ordinary combustibles: wood, paper, cloth, rubber, many plastics","Water (stored pressure or cartridge), foam/AFFF, dry chemical ABC, wet chemical",CO2 is ineffective on deep-seated Class A fires; BC dry powder ineffective,Not applicable (US system),Green triangle with letter A,NFPA 10 (2022),CO2 can knock down surface flames but does not cool burning materials; ABC dry chemical leaves residue but is effective
US (NFPA),B,"Flammable and combustible liquids: petrol/gasoline, oils, solvents, paints, lacquers","Foam/AFFF, CO2, dry chemical ABC or BC, clean agents (e.g. FK-5-1-12/Novec 1230)","Water (jet or spray) — can spread burning liquid and cause steam explosion; not suitable",Not applicable (US system),Red square with letter B,NFPA 10 (2022),Alcohol-resistant AFFF required for polar solvents (alcohols/ketones) — standard AFFF can be broken down by these fuels
US (NFPA),C,Energised electrical equipment,"CO2, dry chemical ABC or BC, clean agents — any non-conductive agent","Water (conductive), foam (conductive) — risk of electric shock to operator",Not applicable (US system),Blue circle with letter C,NFPA 10 (2022),"Class C designation applies only while equipment is energised; once de-energised the underlying fuel becomes Class A or B. NFPA 10 notes the C rating indicates non-conductivity of the agent, not a fuel-type category."
US (NFPA),D,"Combustible metals: magnesium, titanium, sodium, potassium, lithium, zirconium","Specialist Class D dry powder agents (e.g. Met-L-X, Lith-X, copper powder) — agent must match the specific metal","Water (violent or explosive reaction with most combustible metals), CO2 (reacts with some metals), foam, standard dry chemical ABC/BC",Not applicable (US system),Yellow star with letter D,NFPA 10 (2022),"No universal Class D agent exists; the specific extinguishing agent must be matched to the metal hazard. Verify with the extinguisher manufacturer and the SDS for the metal involved."
US (NFPA),K,"Cooking media: vegetable oils and animal fats in commercial cooking appliances",Wet chemical (potassium-acetate or potassium-citrate based),"Water jet (violent steam/splatter), CO2 (insufficient cooling — re-ignition risk), standard ABC dry chemical (ineffective on high-temperature cooking oil fires)",Not applicable (US system),No standard letter symbol; extinguisher labelled Class K,NFPA 10 (2022); also NFPA 17A,"Class K extinguishers are required for commercial cooking equipment hazards. Cooking appliances must have their energy supply (gas or electric) shut off before or during discharge. US Class K broadly corresponds to UK/EU Class F."
UK/EU (BS EN 2),A,"Ordinary combustibles: wood, paper, textiles, rubber, many plastics","Water, foam/AFFF, dry powder ABC, wet chemical","CO2 is ineffective on deep-seated Class A fires; BC powder not rated for Class A",Red band/label (water extinguisher); also cream band (foam); yellow band (dry powder ABC),Not applicable (UK/EU system),BS EN 2:1992+A1:2004; BS EN 3-7:2004+A1:2007,Water extinguisher body is all red (BS EN 3 — no band required for water); colour band on shoulder identifies agent type
UK/EU (BS EN 2),B,"Flammable liquids: petrol, diesel, oils, paints, solvents","Foam/AFFF (cream band), CO2 (black band), dry powder ABC or BC (yellow band), clean agents","Water (jet) — risk of spreading burning liquid; standard water spray not rated for Class B",Cream band/label (foam); black band/label (CO2); yellow band/label (dry powder),Not applicable (UK/EU system),BS EN 2:1992+A1:2004; BS EN 3-7:2004+A1:2007,Alcohol-resistant AFFF required for polar solvents
UK/EU (BS EN 2),C,"Flammable gases: natural gas (methane), propane, butane, hydrogen","Dry powder ABC or BC (can knock down flame — but see note); isolate gas supply first","Water, foam — not effective on gas fires and may create other hazards; CO2 can knock flame but re-ignition risk if gas flow continues",Yellow band/label (dry powder),Not applicable (UK/EU system),BS EN 2:1992+A1:2004,"UK/EU Class C covers flammable gases (unlike US Class C which covers energised electrical). The primary control for a Class C fire is always isolation of the gas supply; extinguisher use without isolation creates re-ignition risk. Electrical equipment fires are addressed through agent non-conductivity ratings in BS EN 3."
UK/EU (BS EN 2),D,"Combustible metals: magnesium, titanium, sodium, potassium, lithium",Specialist Class D dry powder matched to the specific metal,"Water (violent reaction), CO2, foam, standard dry powder ABC/BC",Blue band/label (specialist Class D powder),Not applicable (UK/EU system),BS EN 2:1992+A1:2004,No single universal Class D agent; must match the metal. Verify with manufacturer.
UK/EU (BS EN 2),F,"Cooking media: vegetable oils and animal fats in commercial cooking appliances",Wet chemical (potassium-salt based — canary yellow band/label),"Water jet (violent spattering), CO2 (insufficient cooling for high auto-ignition-temperature oils), standard dry powder (ineffective)",Canary yellow band/label (wet chemical),Not applicable (UK/EU system),BS EN 2:1992+A1:2004; BS 5306-3:2017,"UK/EU Class F broadly corresponds to US Class K. Wet chemical extinguishers react with the hot oil to form a soapy foam layer (saponification) that cools and seals the surface. Cooking equipment energy supply should be shut off before or during use."