Generally a building is broken down into smaller compartments to enable the Firefighters to locate the fire quickly as possible. Even if the system is addressable, it is still considered beneficial to have a separate at a glance indication of the location of the fire. These compartments of a building are called detection zones, which need to comply with the following criteria.
A detection zone should cover no more than 1 storey, unless total floor area is less than 300m₂. Voids in the same fire compartment should be included in the same floor zone.
The maximum floor area of a zone should not be greater than 2,000m₂, except for some large open plan areas that incorporate manual call points only, which can be extended to 10,000m₂
The maximum search distance for the fire fighters to see the seat of the fire within a zone should not exceed 60m assuming the route taken is the worst possible option.
Vertical structures like stairwells, llftwells etc should be considered as separate zones. A manual call point within a staircase should be connected to the zone associated with that floor and ideally be mounted on the accommodation side of the corridor exit. Automatic sensors on the stairwell remain as part of the stairwell detection zone.
An alarm zone is clearly defined within the standard but generally is an area of the building coinciding with the fire compartment boundaries.
There must be a clear break between these alarm zones to ensure alert and evacuation messages are not overheard from adjacent areas. The only other criteria is that an alarm zone may consist of a number of detection zones but not vice versa.
Alarm zones are only required when phased or staged evacuation is required. II is therefore Important that care should be taken to ensure only one message is heard at any one time particularly where two alarm zones are attached.