Fire alarm categories explained

Category M — manual call points only

The simplest category: manual call points (break-glass units) at exits and escape routes, with no automatic smoke or heat detection at all. Someone has to see or smell the fire and raise the alarm themselves — there’s no early warning if a fire starts when no one’s nearby. Often found in very low-risk, well-supervised premises, sometimes alongside a higher category in specific areas.

Category L — protecting life

L-category systems are designed primarily to give people time to escape safely.

• L1 — detectors in all areas of the building. The highest level of life protection.
• L2 — all L3 areas plus additional high-risk rooms (e.g. boiler rooms, plant rooms).
• L3 — escape routes plus rooms opening onto them, warning occupants before routes become impassable.
• L4 — escape routes only (corridors and stairways) — a basic level of early warning.
• L5 — a custom design to meet a specific objective identified in a Fire Risk Assessment.

Category P — protecting property

P-category systems are designed primarily to limit property damage and business interruption by calling the fire brigade as early as possible.

• P1 — detectors throughout the whole building.
• P2 — detectors in specific, defined high-risk areas only.

Which category do I need?

This depends on your building’s use, layout and your fire risk assessment — it’s not something to guess at. Many buildings combine categories (for example, L2 with property protection in a specific plant room).