Fire alarm systems are designed with one of three considerations at their core, Category M, Category L and Category P.
Category M systems are manual systems that incorporate no automatic fire detectors.
Category L systems are automatic fire detection systems designed for the protection of life; these are normally specified as a result of a fire risk assessment and specific building regulations.
L1Systems installed throughout all areas of the building
L2Systems installed only in defined parts of the building, including all parts necessary to satisfy the recommendations of the code for a Category L3 system. The additional areas protected, over and above those protected in a Category L3 system, are those in which there is either a high likelihood of fire starting or a high risk to life if a fire does start.
L3Systems designed to give warning of fire at an early enough stage to enable all occupants other than, possibly those in the room of fire origin, to escape safely before the escape routes are impassable due to the presence of fire, smoke or toxic gasses. To satisfy this objective, other than in the case of very short corridors, fire detectors need to be installed in all rooms or areas that open into the escape routes.
L4Systems installed within those parts of the escape routes comprising circulation areas and circulation spaces, such as corridors and stairways.
L5Systems in which the protected area(s) and/or the location of detectors is designed to satisfy a specific fire safety objective (other than that of a Category L1, L2, L3 or L4 systems).
Category P systems are automatic fire detection systems intended for the protection of property.
P1Systems installed throughout all areas of the building
P2Systems installed only in defined parts of the building.