BS5839-1 Fire Alarm System Classifications

BS5839 Splits fire alarm systems into 3 categories, P, L & M.

All the systems described below are expected to have manual call points on all doorways to air, entrances to stairwells, change of zone and corridors where persons are not expected to walk more than 45 metres to operate a call point.

All classifications should have sounders positioned throughout the building to achieve a minimum sound pressure of 65dB, within sleeping areas 75dB at bedhead and in areas of high ambient noise sound levels the fire alarm sound levels should be 5dB above the normal noise level, although not exceeding 120dB. It is comman practice to install strobes in all loud areas as ear protection may be in use.

Category P Fire Alarm Systems

BS5839 Category P Fire Alarm Systems are designed specifically for protection of property only.  Category P systems are split into 2 classifications P1 or P2.

The main objective of a Category P1 fire alarm system is to provide the earliest possible warning of a fire to minimise the time between ignition and the arrival of the fire fighters.

The difference between a P1 and a P2 system is that a P1 system is designed to protect the whole building, whereas a P2 system is installed in defined parts of the building only.  These defined parts of the building may be areas with an extraordinary high fire risk or hazard.

P systems usually have external strobe/sounders, remote notification via an Alarm Receiving Centre and are usually a result of an insurance request.

Category L Fire Alarm Systems

The main objective BS5839 Category L Fire Alarm System is life protection.

These systems are split into five classifications L1 to L5.

BS5839 Classification: L5

A BS5839 Classification L5 System is designed for buildings that have a particular fire risk identified which warrants some special attention. For example, if there is an area of high fire risk which is considered worthy of having some automatic detection but a manual system is also needed, then this will be termed as L5/M.

BS5839 Classification: L4

Automatic fire detection on escape routes only.

BS5839 Classification: L3

Automatic fire detection on escape routes and adjoining rooms.

BS5839 Classification: L2

Automatic fire detection on all escape routes and rooms leading onto escape routes.
An L2 system can also include additional areas deemed as a high risk not included in the escape routes and adjoining rooms, such as boiler or plant rooms.

BS5839 Classification: L1

Automatic fire detection in all rooms, on all escape routes and in all voids over 600mm deep (assessed as a risk).

All of the above classifications can have an additional rating, I.E. L3 +Void  or  M +High Risk.

Category M Fire Alarm Systems

A manual operation only system, with call points on all doorways to air, entrances to stairwells and corridors where persons are not expected to walk more than 45 metres to operate a call point. This system is usually only accepted where a remote (non-visible) fire could not block your exit or cause harm.