Kerova

Checker · Fire alarm · BS 5839-1

Fire alarm zone checker

Enter the floor area of a storey to see the fewest zones it needs. If you have a zone's floor area or its search distance, enter them to check them against the limits. Leave those two blank to skip.

Your figures

m²
m²

The floor area of one zone you want to check.

m

The longest walk into the zone before evidence of a fire is visible.

Result

Enter the storey floor area to see the result.

Working

fewest zones = roundup(storey floor area ÷ 2000 m²)

  • A detection zone is at most 2,000 m² of floor area.
  • The search distance is how far someone walks into a zone, from where they enter, before they can see evidence of a fire. It should not be more than 60 m. That is the figure given for conventional (non-addressable) zones.
  • A zone normally covers one storey. Stairways and lift shafts are separate zones.
  • The 2025 edition expects a zone plan wherever there is more than one zone on a storey.

Source: BS 5839-1, as set out in the FIA guide to the 2025 edition and panel makers' design guides. The 2,000 m² figure comes from one 2025 maker's guide, and older guides agree. Some guides also list exceptions: a zone may cover more than one storey if the total floor area is under 300 m², and a large open plan area with call points only may be up to 10,000 m². Those come from the same guide and older ones, and were not found quoted from the standard, so they are not used in the checks.

This gives the fewest zones, not the best layout. Zones should follow how the building is used and where people search, not just the area limit.

For guidance only. Always check against the current edition of the standard and the manufacturer's data.

Built by the engineer behind Kerova, certificate software for fire and security firms.