System design

Category M systems are manual systems which rely on the occupants on the building discovering the fire and operating the system to warn others. Such systems are a basic requirement in places of employment with no sleeping risk. 

In addition to manual means of triggering an alarm, L category systems will also normally have an element of coverage using automatic fire detection such as smoke or heat detectors.

Category L5 systems are the 'custom' category and relate to certain special requirements that cannot be covered by any other category. Where such systems are specified, careful reference must be made to the objective of the cover, normally from a fire risk assessment.

Category L4 systems cover escape routes and circulation areas only. Detectors might be sited in other areas of the building, but the objective is to protect the escape routes. 

Category L3 systems provide more extensive cover than Category L4 ensuring rooms leading onto escape routes are also covered. The objective is to warn the occupants of the building early enough to ensure that all are able to exit the building before escape routes become impassable. 

Category L2 systems relate to automatic fire protection in defined areas of the building as well as satisfying the requirements of Category L3. The wider cover relates to parts of the building considered to have a high level of risk or fire hazard. 

With Category L1 systems, the whole of a building is covered with minor exceptions.

Category P1 systems are installed throughout the building -the objective being to offer the earliest possible warning of fire to minimise the time between ignition and the arrival off fire fighters.

Category P2 systems provide fire detection in specified parts of the building where there is either high risk or where business disruption must be minimised.