What are the fire classes in the UK?
Fires are classified in the UK based on what is burning.
Understanding fire classes is essential for choosing the correct fire extinguisher — and avoiding actions that could make a fire far more dangerous.
This guide explains each UK fire class (A–F), what causes them, and why the wrong extinguisher can put lives at risk.
🟩 🔥 Class A — Fires involving solid materials
What causes them:
Class A fires involve solid combustible materials such as wood, paper, cardboard, textiles, furniture and packaging.
These fires burn with embers and require extinguishers that cool the burning material.
Why the wrong extinguisher is dangerous:
Using an extinguisher that does not cool the fire (such as CO₂ alone) can allow embers to re-ignite after the fire appears to be out.
🟥 🛢️ Class B — Fires involving flammable liquids
What causes them:
Flammable liquids such as petrol, diesel, oils, solvents, paints and alcohols.
These fires spread rapidly across surfaces and can reignite easily.
Why the wrong extinguisher is dangerous:
Using water can cause burning liquid to spread, dramatically increasing the size and intensity of the fire.
🟦 💨 Class C — Fires involving flammable gases
What causes them:
Gases such as natural gas, propane, butane and methane.
These fires often involve pressurised fuel sources.
Why the wrong extinguisher is dangerous:
Extinguishing a gas flame without isolating the supply can lead to re-ignition or explosion.
🟨 🧲 Class D — Fires involving flammable metals
What causes them:
Combustible metals including lithium, magnesium, sodium and potassium.
These fires burn at extremely high temperatures and react violently with many common extinguishing agents.
Why the wrong extinguisher is dangerous:
Water, foam, CO₂ and standard powder extinguishers can cause violent reactions or explosions.
Only specialist Class D metal powder extinguishers are suitable.
⬛ ⚡ Class E — Electrical fires (UK usage)
What causes them:
Fires involving live electrical equipment such as appliances, machinery, servers and wiring.
Electricity itself does not burn, but presents a serious shock hazard.
Why the wrong extinguisher is dangerous:
Using conductive extinguishers can cause electric shock or electrocution.
Once power is isolated, the fire should be treated according to the underlying fuel class.
🟪 🍳 Class F — Fires involving cooking oils and fats
What causes them:
High-temperature cooking oils and fats, typically in commercial kitchens and deep fat fryers.
These fires burn extremely hot and can reignite rapidly.
Why the wrong extinguisher is dangerous:
Water or CO₂ can cause violent fireballs and severe injury.
Wet chemical extinguishers are specifically designed to cool and chemically suppress these fires safely.
Summary of UK fire classes
| Class | Involves | Key danger if misused |
|---|---|---|
| 🟩 A | Solid materials | Re-ignition if not cooled |
| 🟥 B | Flammable liquids | Fire spread with water |
| 🟦 C | Flammable gases | Explosion or re-ignition |
| 🟨 D | Flammable metals | Violent chemical reactions |
| ⬛ E | Electrical equipment | Electric shock |
| 🟪 F | Cooking oils and fats | Fireballs and rapid spread |
Final guidance
Understanding fire classes is fundamental to fire safety.
Using the correct extinguisher can prevent injury, property damage and escalation — while using the wrong one can be catastrophic.