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The main causes of fire are
- open flames
- hot surfaces
- electrical overheating
- electrical arcing and sparking
- sparks from tools
- friction
- spontaneous heating (for example mixing the wrong chemicals
together) - sparks from welding and cutting
- carelessly discarded smoking materials or matches
- static electricity and explosions
Extinguishing agents and classification of fires
Before a fire can occur three things are necessary: fuel, heat and oxygen.
These three factors are often referred to as the triangle of combustion. If you remove one factor, the triangle collapses and there can be no fire.
![](https://www.etutor.org.uk/downloads/l3healthandsafety/fire.png)
Fires are classified into five categories according to the fuel type and the means of extinguishing.
![](https://www.etutor.org.uk/downloads/l3healthandsafety/fireclass.png)