BS 5306-8 gives a method for working out extinguisher provision, and the fire risk assessment refines it for the building. The basics are straightforward.
Class A coverage
For ordinary combustibles (paper, wood, textiles) the standard requires a minimum of two Class A extinguishers on every floor with a combined rating of at least 26A, unless the floor is very small. The total A rating should be at least 0.065 multiplied by the floor area in square metres. Nobody should have to travel more than 30 metres to reach one. A typical 9-litre water or 6-litre foam extinguisher is rated 13A, so two per floor is the usual minimum.
Special risks
| Risk | Extinguisher |
|---|---|
| Electrical equipment, server rooms, switchrooms | CO2 (2 kg or 5 kg) |
| Commercial kitchens with deep fat fryers | Wet chemical (Class F) plus fire blanket |
| Flammable liquids, workshops, plant rooms | Foam (fluorine-free) or dry powder |
| Vehicles, outdoor plant, gas | Dry powder |
| E-bike and scooter stores, battery rooms | Lithium-ion battery extinguisher and specialist advice |
The three common mistakes
- Dry powder indoors. It is effective but the cloud blinds and chokes in enclosed spaces; BS 5306-8 discourages it inside except where nothing else will do.
- Extinguishers mounted where nobody can see them, or on the floor behind a door. They belong on exit routes, at conspicuous positions, at a consistent height, with a location sign.
- Missing the annual service. An out-of-date extinguisher is a finding on every fire risk assessment and, after use, may not work.