Standard explained
Fire Alarm Categories Explained
BS 5839 classifies fire alarm systems by category — M (manual), L (life protection) and P (property protection) — each with sub-categories for coverage.
BS 5839 classifies fire alarm systems by category, according to whether they protect life or property, and how much of the building they cover. The category is chosen from the fire risk assessment.
The main categories
- Category M — a manual system: detection relies on people operating call points. No automatic detectors.
- Category L — systems for the protection of life, with automatic detection. Sub-divided L1 to L5 by the extent of coverage (L1 being detection throughout, down to more targeted coverage).
- Category P — systems for the protection of property, sub-divided P1 (throughout) and P2 (defined areas). See P1 and P2 systems.
Why category matters
The category determines where detectors and call points go and therefore the cost, coverage and level of protection. Installing a category below what the risk assessment requires leaves people or property under-protected; installing far above it wastes money.
Getting the category right
The correct category flows from a competent fire risk assessment of the building, its occupants and its use. Once set, the system must be maintained to that specification — see periodic servicing.
Related service
Fire Alarm Testing
Inspection and testing of fire detection and alarm systems in line with BS 5839 good practice.
Learn moreMore in this topic
Standard explained
BS 5839 Overview: Fire Alarm Standard
BS 5839 is the UK code of practice for fire detection and alarm systems, covering design, installation, commissioning and maintenance in non-domestic premises.
Learn moreStandard explained
Fire Detector Types Explained
Fire detector types include optical (smoke), heat, multi-sensor and aspirating detectors — each suited to different environments and fire risks under BS 5839.
Learn moreKnowledge article
Reducing Fire Alarm False Alarms
Reduce fire alarm false alarms by choosing suitable detectors, siting them well, maintaining the system, and managing activities like cooking, steam and dust.
Learn moreKnowledge article
Fire Alarm Testing Explained
Fire alarm testing confirms a fire detection and alarm system will detect fire and warn occupants — carried out and maintained to BS 5839.
Learn moreThis article provides general guidance and distinguishes legislation, British Standards and good practice. It is not legal advice. Always confirm the specific duties applying to your property and tenure.