Fire alarm design

When designing fire alarm systems whether be wireless fire alarms, addressable fire alarms or conventional systems, in accordance with fire code BS5839-1, fire detection in the form of fire detectors should be mounted at least 500mm away from walls or ceiling obstructions greater than 250mm deep and at least twice the depth of obstructions less than 250mm deep.

The detectors should also be mounted at least 1m away from any forced air inlet. Where the obstruction is greater than 10% of the height of an area it should be considered as a wall. Similarly a floor mounted obstruction (such as racking) should be considered a wall if it
comes to within 300mm of the height of the detector.

When designing fire alarm system where fire detection is required in vertical shafts, such as stairwells, a smoke detector should be mounted at the top of the shaft and within 1.5m at each level.

However, when designing wireless fire alarm systems, the fire code now used is EN54.