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Fire Extinguisher Calculator
Work out the minimum fire rating and extinguisher count for Class A (ordinary combustibles) cover, from floor area, per BS 5306‑8.
Covers Class A provision only. Confirm final selection against a fire risk assessment and the current edition of BS 5306‑8.
Methodology
How this is calculated.
BS 5306‑8 sets the minimum Class A (ordinary combustibles) fire rating for a storey as 0.065 × the floor area in m², with a floor‑wide minimum of 26A. That minimum drops to 13A for an upper floor of a single‑occupancy building of 100 m² or less.
A minimum of two extinguishers is required per storey, reduced to one where the floor area is 50 m² or less. The required A‑rating can be met with any combination of extinguisher ratings that totals it — this calculator suggests a count of 13A units as one practical way to meet the figure, not the only one.
Maximum travel distance to the nearest extinguisher is 30m for Class A and C risks, and 10m for Class B, electrical, and Class F risks.
Class B (flammable liquids), electrical, and Class F (cooking oils/fats) provision is sized against the specific hazards present on site — equipment, quantities, storage — rather than floor area, so it isn't covered by this calculator. A full provision plan should be based on a fire risk assessment covering all the hazard classes actually present in the building.
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