All buildings should have arrangements for detecting fire and raising the alarm. In most buildings, fires are detected by people, either by sight or smell, and therefore often nothing more is needed.
In some small buildings/premises, the means of raising the alarm may be simple (for example,a shouted warning). In assessing appropriate solutions, warnings need to be heard and understood throughout the premises.
Other than for some small buildings / premises, an electrically operated fire alarm system should be provided. In some situations, the alarm should be operated by a fire detection system. The detailed specification should be compatible with the fire strategy for the building.
NOTE: The term 'fire alarm system' describes the combination of components for giving an audible and/or other perceptible warning of fire.
NOTE: In this document, the term 'fire detection system' describes any type of automatic sensor network and associated control and indicating equipment. Sensors may be sensitive to smoke, heat, gaseous combustion products or radiation. Automatic sprinkler systems can also be used to operate a fire alarm system.
In 'residential (institutional)' and 'residential (other)' occupancies (purpose groups 2(a) and 2(b)), automatic fire detection and alarms should be provided.
Automatic fire detection and alarms should be provided in non-residential occupancies where a fire could break out in an unoccupied part of the premises (e.g. a storage area or a part of the building that is not visited on a regular basis) and prejudice the means of escape from occupied part(s) of the premises.
Automatic fire detection will also be necessary where fire protection systems, such as pressure differential systems or door releases, need to operate automatically.
Every building design should be assessed individually. General guidance on the category of fire detection system that may need to be provided within a building can be found in Table A1 ofBS 5839-1.
Where an electrically operated fire detection and alarm system is provided, it should comply with BS 5839-1 .
BS 5839-1 specifies three categories of system:
Category L systems are divided into the following.
L1 - systems installed throughout the protected building.
L2 - systems installed only in defined parts of the protected building (a category L2 system will normally include the coverage required of a category L3 system).
L3 - systems designed to warn of fire at an early enough stage to enable all occupants, other than possibly those in the room where the fire started, to escape safely before the escape routes become impassable because of fire, smoke or toxic gases.
L4 - systems installed within those parts of the escape routes that comprise circulation areas and circulation spaces, such as corridors and stairs.
L5 - systems in which the protected area(s) and/or the location of detectors are designed to satisfy a specific fire safety objective (other than that of a category L1, L2, L3 or L4 system).
Type P systems are divided into the following.
P1 - systems installed throughout the protected building.
P2 - systems installed only in defined parts of the protected building.