Fire classes A–K: US and European systems compared
Two systems — US NFPA 10 and the European EN 2 standard — use different letter codes for the same types of fire. Using the wrong extinguisher is dangerous. This reference explains both systems side-by-side.
Side-by-side comparison
All fire classes at a glance
The letter is only part of the story — the extinguisher type matters most.
| Class | US NFPA meaning | EN/UK meaning | Correct extinguisher |
|---|---|---|---|
| A | Ordinary combustibles — wood, paper, cloth, plastics | Same as US — ordinary combustibles | Water, foam, ABC dry powder |
| B | Flammable liquids — petrol, oil, paint, solvents | Same as US — flammable liquids | CO₂, foam, dry powder |
| C | Energised electrical equipment (US only) | Flammable gases — LPG, acetylene, methane (EN only) | US: CO₂, dry powder · EN: dry powder (cut supply first) |
| D | Combustible metals — magnesium, lithium, sodium | Same as US — combustible metals | Specialist dry-powder (L2, M28, Met-L-X) |
| E | Not used in NFPA system | Not in current EN standard (was electrical in older codes) | — |
| F / K | K: Cooking oil and fat (commercial kitchens) | F: Cooking oil and fat (domestic and commercial) | Wet chemical (Class K / Class F rated) |
Class C is the most important divergence — electrical fires in the US, gas fires in Europe. Always confirm which system applies to your region before purchasing equipment.
The critical difference: Class C
In the US, Class C means an energised electrical fire — a fire involving live equipment. The correct response is a non-conducting agent such as CO₂ or dry chemical. Crucially, electricity is the ignition source, not the fuel. Once the power is cut, the fire is reclassified by whatever is burning (usually Class A for plastic components, or Class B for oil-cooled transformers).
In Europe and the UK, Class C means flammable gases — LPG, acetylene, natural gas. Electrical fires do not have their own class under EN 2; the guidance is simply to cut the power and treat the remaining fire as Class A or B. The EN 2 standard reflects the position that electricity is not a material that burns.
Class K vs Class F: cooking fires
Cooking oil fires in deep fryers require a wet-chemical extinguisher. The agent reacts with the hot fat in a process called saponification, forming a soapy blanket that cools and seals the oil surface. A standard ABC dry-powder extinguisher is ineffective on deep fryer fires — the powder cannot cool the oil mass and the fire will re-ignite once the powder cloud settles. In the US this extinguisher carries a Class K rating (NFPA 10); in the UK it carries a Class F rating. Both refer to the same type of fire and the same extinguisher agent.
Practical rule
When you see an extinguisher class letter, always check which country's system it references. If you are unsure, use the Extinguisher finder tool — it asks for your region and shows the correct class label and colour band for your location.
Primary sources: NFPA 10 (2022) · BS EN 2:1992+A1:2004 · UK workplace fire safety guidance
Fire classes FAQ
Common questions about fire classification
The two systems evolved independently. In the US NFPA 10 system, Class C was assigned to energised electrical fires because "C" for "circuit" was a logical mnemonic. In the European EN 2 standard, the letters were assigned in alphabetical order across fuel types, and gases came third. This is the single most common source of confusion in international fire safety training.
A wet-chemical extinguisher is specifically designed for cooking oil and fat fires. It works by reacting with the hot oil to form a soapy foam layer that seals the surface and prevents re-ignition — a process called saponification. In the US, wet-chemical extinguishers are rated K. In the UK and Europe they carry a Class F rating. Standard ABC dry-powder extinguishers are not effective on deep-fat fryer fires. Use the Extinguisher finder to check what your kitchen needs.
In the US NFPA system, Class E does not exist — electrical fires are Class C. In some older European classifications, Class E was used for electrical fires, but the current EN 2 standard does not include a Class E, because electricity is not a fuel — it is an ignition source. When the power supply is cut, an electrical fire becomes a Class A, B or C (gas) fire depending on what is burning.
Class D fires involve combustible metals — magnesium, titanium, sodium, potassium, lithium and similar. They are rare in everyday settings but occur in metal-processing facilities, laboratories, and with lithium-ion battery fires. They require a dry-powder agent specifically rated for metal fires (not a standard ABC powder, which can react dangerously with some metals). The NFPA 484 standard covers combustible metals in detail. Note that e-bike and e-scooter batteries also carry lithium-ion risks — see our e-bike battery fire risks guide.