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BS 5839‑1 Category Table
Quick reference for the M, L1–L5 and P1–P2 system categories and what each is designed to cover.
| Category | Coverage |
|---|---|
| M | Manual system — call points and sounders only, no automatic detection. Relies on occupants raising the alarm themselves; suited only to buildings that are fully occupied and alert whenever in use. |
| L1 | Automatic detection throughout — virtually every room, void and space in the building, including roof voids over 800mm. The most comprehensive life‑safety category, giving the earliest possible warning even to occupants in the room where the fire starts. Used for higher‑risk sleeping premises such as large hotels and care homes. |
| L2 | As L3, plus specific high‑risk rooms elsewhere in the building (kitchens, plant rooms) where a fire is likely to originate but which don't open directly onto an escape route. Used for premises such as mid‑size hotels and HMOs. |
| L3 | Escape routes plus every room that opens directly onto them, so a fire is detected before it can block the route out. A common minimum where occupants may be asleep — offices, schools, and smaller sleeping premises. |
| L4 | Escape routes only — corridors, stairways and lobbies — giving warning that the escape route itself is compromised. A lower baseline, often used for smaller or lower‑risk occupied buildings. |
| L5 | A bespoke category designed to meet a specific fire safety objective not covered by L1–L4 — for example protecting a single high‑value or high‑risk room. Scope is defined case by case, usually from a fire risk assessment finding or an insurer requirement. |
| P1 | Property protection, whole building — automatic detection throughout the premises (comparable coverage to L1), purely to protect property and business continuity, typically with automatic signalling to an Alarm Receiving Centre. |
| P2 | Property protection, defined areas only — automatic detection in specific high‑value or high‑risk parts of the premises, such as server or comms rooms, rather than the whole building. |
L2, L3 and L4 are nested — each adds coverage on top of the one below it. L1 covers everywhere; L5 is a one‑off bespoke scope defined by risk assessment rather than a fixed area rule. P1 and P2 follow the same "everywhere vs. defined areas" logic, for property rather than life protection.
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