When the need for a fire alarm system is established either by fire risk assessment or Fire Authority recommendation, it should be established what category the fire alarm system should be installed to. This will vastly depend on the type, size and use of the premises, weather or not the building will be used as sleeping accommodation or other higher risk activities will be conducted within it. Below is a guide to the fire alarm categories as defined in BS5839:1-2017.
BS 5839-1 defines eight categories of system, according to whether the system is purely manual or
incorporates automatic fire detection, and, in the latter case, the purpose and extent of the automatic
fire detection.
The eight categories of system are defined as follows:
Category M systems: These are manual systems and therefore, incorporate no automatic fire detectors.
Category L systems: These are automatic fire detection systems intended for the protection of life. They are further subdivided into the following subcategories of system...
Category L1: Systems installed throughout all areas of the building.
Category L2: Systems 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 high likelihood of fire starting or a high risk to life if fire does start.4 of 11 Guidance on Fire alarm Categories
Category L3: Systems 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 gases. 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 onto the escape routes.
