Fire Alarm detection Zones

6.2 Detection Zones
Fire Alarm systems have fire detection zones that are essentially a convenient way of dividing up a building to assist in quickly locating the position of a fire.

The fire alarm zone boundaries are not physical features of the building,
although it is normal to make the zone boundary coincide with
walls, floors and specifically fire compartments. The size and
position of the fire detection zones will therefore tend to be dependant
on the shape of the buildings, but will also depend on what the
building is used for and to some extent the number of people the
building is expected to contain at any one time.

When designing a fire alarm system, whether it be a convention, wired addressable or a wireless fire alarm system, taking account of the fire zones in accordance with BS 5839-1 is important.
BS 5839-1 has some specific recommendations with respect to
detection zones:
- Zones should be restricted to single floors, except where the
total floor area of a building is less than 300m2
- Voids above or below the floor area of a room may be
included in the same zone as the room so long as they are
both in the same fire compartment
- Zones should not be larger than 2000m2 except for manual
systems in single storey open plan buildings, such as a
warehouse, where up to 10000m2 is allowed
- When it come to fire detection, fire detectors in an enclosed stairwell, lift shaft or the like should be considered as a separate zone
- The search distance within a zone should be less than 60m
(all possible entrance points must be considered). This can be
relaxed when using addressable fire alarm or wireless addressable fire alarms, if the information
provided at the control and indicating equipment would allow
fire fighters, unfamiliar with the building, to proceed directly to
the location of the fire. The search distance only relates to the
distance from entering a zone to being able to determine the
location of the fire, it is not necessary to travel to the fire
- Zones should not cross fire compartments, a fire compartment
can contain several zones but a zone should not contain more
than one fire compartment