Quick comparison
Match the class to what is burning
The same ignition source can produce different fire classes once materials become involved. Read the certified markings on the extinguisher rather than relying on body colour or a generic poster.
| Class | Fuel or material | Common examples |
|---|---|---|
| A | Solid materials, normally organic | Wood, paper, textiles and many furnishings |
| B | Flammable liquids or liquefiable solids | Petrol, solvents, paint and some plastics |
| C | Flammable gases | Propane, butane and methane |
| D | Combustible metals | Magnesium, sodium and other specific metal risks |
| F | Cooking oils and fats | Commercial fryers and high-temperature cooking media |
| L | Lithium-ion batteries under ISO 3941:2026 | Rechargeable cells and battery packs within the standard’s definition |
Common confusion
Electrical equipment is not the underlying fuel class
Electricity creates shock, arc and re-energisation hazards. While equipment remains live, only equipment specifically suitable for that situation should be considered. After safe isolation, the burning insulation, plastic, oil or other material determines the underlying class.
CO₂ is commonly selected for certain electrical risks because it leaves no residue, but it has limited cooling and can allow re-ignition. The correct provision depends on the equipment, enclosure, people and escape route.
Product performance
The class letter is only the start of the rating
Portable extinguishers carry tested ratings that indicate performance on defined test fires. Two extinguishers of the same agent and nominal capacity may not have the same rating.
Selection therefore considers both class and rating, together with floor area, travel distance, special hazards and the consequences of discharge. A premises matrix should not be used as a ready-made specification.
Practical next step
Turn the classification into a premises-specific provision
Identify fuels and processes through the FRA, confirm the class and scale of each hazard, then select certified equipment with competent advice. Review after new batteries, cooking, gases, workshop processes or storage are introduced.
- Identify every relevant fuel and process
- Check the extinguisher label and certified rating
- Consider people, visibility, contamination and escape
- Provide specialist agents for specialist hazards
- Record selection, siting, checks and maintenance