Fire Classifications
Class A fires – Involve freely burning organic solid materials like paper, wood, textiles and other carbonaceous materials.
Class B fires – Are of flammable liquids such as petrol and spirits, but not alcohol or cooking oil.
Class C fires – involve flammable gases such as propane and butane.
Class D fires – are fires involving burning metals such as magnesium or lithium (think rechargeable battery packs).
Class F fires – involve fats, such as cooking oil, lard or butter.
Electrical fires – are fires caused by faults in electrical equipment, though these can fall into any of the classifications as it’s the stuff near the electric source which is burning, not the power itself.
Types of Extinguishers
There are seven types of extinguisher in use, based on the content they expel to fight the fire: Water – these are the classic Signal Red extinguisher seen most often and should only be used on Class A fires.
- Water Mist – these are white and red and can be used on Classes A, F, B and C, as well as electrical fires if they’ve been dielectrically tested and are dispensing deionised water.
- Foam – these are suitable for Classes A and B fires, plus electrical ones if the contents have been dielectrically tested.
- Dry Powder – suitable for Classes A, B and C, plus electrical fires.
- Carbon Dioxide – suitable for Class B and electrical only.
- Wet Chemical – suitable for Classes A and F, as well as some Class B fires.
- Specialist Powder – these should only be used on Class D fires.
Fire Rating
All extinguishers suitable for Class A, B or F fires carry a fire rating shown by a number and letter e.g. 13A. The number shows the size of fire it was found to extinguish well under test conditions. The larger the number, the larger the fire it can extinguish.
The letter indicates the fire classification. Classes C, D and extinguishers for electrical fire don’t have a number rating for those types of fire.