Pick a class of fire above.
The three ways a fire goes out
Every extinguisher removes one side of the fire triangle: heat, oxygen or the chemical chain reaction in the fuel.
- Cooling. Water takes the heat out of a solid fuel. It is the cheapest and most effective choice for paper, wood and fabric, and the most dangerous choice for anything else.
- Smothering. Foam, CO<sub>2</sub>, wet chemical, powder and a fire blanket all cut the fire off from oxygen in different ways. CO<sub>2</sub> is clean and safe on electrics but does not cool, so watch for re-ignition.
- Interfering with the chemical reaction. Specialist D powder stops the reaction inside a burning metal. Nothing else works on those fires.
The table, class by class
| Class | What burns | Water | Foam | CO<sub>2</sub> | ABC Powder | Wet Chemical | D Powder |
|---|---|---|---|---|---|---|---|
| A | Solids: paper, wood, textiles | Yes | Yes | Yes | Yes | ||
| B | Flammable liquids: petrol, diesel, oil | Yes | Yes | Yes | |||
| C | Flammable gases: natural gas, propane | Yes | |||||
| D | Combustible metals: sodium, potassium, lithium | Yes | |||||
| F | Cooking oils and fats: deep fat fryers | Yes | |||||
| Electrical | Short-circuiting equipment | Yes | Yes |
Before you pick anything up
- Raise the alarm first. On most sites your job is to get people out and call the fire service; tackling a fire is only ever for something small, in its early stage, with a clear exit behind you.
- Read the label. UK extinguishers are red with a coloured band: cream for foam, black for CO<sub>2</sub>, blue for powder, yellow for wet chemical. The label lists the classes it is rated for.
- PASS. Pull the pin, Aim at the base of the fire, Squeeze the handle, Sweep side to side.
- If in doubt, get out. Close the door behind you.
Fire safety is covered in the first unit of the Door Supervisor and Security Guard courses. The practice questions in the Door Supervisor exam guide include extinguisher questions.
FAQ
Which fire extinguisher is used for electrical fires?
CO<sub>2</sub> or ABC powder. Never water, foam or wet chemical on live equipment, because they conduct electricity.
What is a Class F fire?
A fire involving cooking oils or fats, typically a deep fat fryer. Only a wet chemical extinguisher, or a fire blanket for a small pan, is suitable. Water makes it explode outward.
What colour band is a CO2 extinguisher?
Black. Foam is cream, powder is blue, wet chemical is yellow and water has a plain red body.
Can you use a powder extinguisher indoors?
ABC powder is rated for most fires, but in a small enclosed space the cloud reduces visibility and can be inhaled, and the residue damages electronics. Use it where you have to, then ventilate.