Understanding BS 5839-1 alarm categories is essential. We explain each category and when to specify them.. BS 5839 1 Categories L1 — Full life protection coverage (all areas) L2 — Coverage of defined areas beyond escape routes L3 — Coverage of escape routes only L4 — Coverage within escape routes of circulation areas only L5 — Engineered system for specific requirements P1 — Full property protection coverage P2 — Coverage of defined high risk areas only M — Manual call points only For fire alarm system design, contact us.