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    Fire Alarm Categories

    Categories of fire alarm system for Domestic and Commercial Premises

    The Categories (Non domestic premises) BS5839-1

    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.

    Category M systems:

    These are manual systems and therefore, incorporate no automatic fire detectors.

    M Fire Alarm System

    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 as follows:

    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.

    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.

    Category L4:
    Systems installed within those parts of the escape routes comprising circulation areas and circulation spaces, such as corridors and stairways.

    Category L5:
    Systems 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 system).


    Category P systems:

    These are automatic fire detection systems intended for the protection of property. There are then two subcategories, namely:

    Category P1:
    Systems installed throughout all areas of the building.

    Category P2:
    Systems installed only in defined parts of the building.

    The Categories (Domestic premises) BS5839-6 has categories but also has grades.

    The categories for life safety are LD1, LD2 and LD3.

    LD3 requires detection on escape routes (usually stairs and lobbies), LD2 also requires detection in areas of high fire risk (usually kitchens and lounges) and LD1 requires detection in all parts of the building. None of these categories require controls or Call Points.

    BS 5839-6 describes six grades from A to F.

    The grades of system essentially refer to the level of sophistication of the system. Grade A is broadly a system like the type described in BS5839-1, with controls, detectors (rather than smoke alarms) and alarms. Grade B and C are similar but with simpler controls and may use smoke alarms or discreet detectors and alarms. Category D, E and F describe systems comprising one or more smoke alarms, usually within one dwelling (e.g. one flat). Grade F refers to battery operated smoke alarms. Grade E refers to mains only smoke alarms. Grade D refers to mains operated smoke alarms with a reserve power supply such as batteries (rechargeable or non-rechargeable) or capacitor which is capable of supporting the smoke alarm if the mains electricity fails. Grade D is generally preferred and Grade E and Grade F may not be acceptable to the authorities in many situations.


    Since there are a number of different categories defined and in a domestic premises the addition of grades as well, a reference to BS 5839-1 or 6 without a reference to a system category and (grade if domestic), for example, in a purchase specification; enforcement notice under fire safety legislation; or a fire risk assessment would be virtually meaningless. Within statutory requirements imposed by enforcing authorities – as part of any requirements imposed by property insurers and in any action plan of a fire risk assessment – the category of system to be installed and grade (if applicable) should always be included in a specification.


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