Fire detection & alarm systems: a responsible person's guide
Under the Fire Safety Order you must give your building an appropriate means of detecting fire and warning people. BS 5839-1 is how that's done properly — and how an inspector will judge whether you've done it.
The legal duty
Article 13 of the Fire Safety Order requires appropriate fire detection and a means of warning, kept in working order, with records to prove it. For non-domestic buildings, the design and maintenance standard is BS 5839-1. Your fire risk assessment decides what "appropriate" means for your building — and you have to be able to justify the choice.
The categories: matching the system to the building
BS 5839-1 sorts systems into three families. The right one comes from your risk assessment, not a catalogue.
- Category M — manual. Break-glass call points only, no automatic detection. It relies on a person spotting the fire, so it's only suitable where the building is always occupied when at risk.
- Category L — life protection (automatic detection to protect people):
- L1 — detection throughout the building; the highest level.
- L2 — escape routes, the rooms opening onto them, plus identified high-risk areas.
- L3 — escape routes and the rooms opening onto them. A common, sensible workplace standard: it warns you before a fire in an office reaches the corridor.
- L4 — escape routes only.
- L5 — a bespoke system targeting one specific risk identified in the assessment.
- Category P — property protection. P1 (throughout) or P2 (high-risk areas), usually driven by insurers. Often combined with a life system — an office might be specified L2/P1.
2025 update: rooms where people sleep are treated as high-risk and need smoke detection, not heat detectors — they don't warn a sleeping person quickly enough.
Getting the detector right
Optical smoke detectors suit escape routes and general areas; heat detectors belong in kitchens and dusty or steamy spaces where a smoke detector would false-alarm; multi-sensor detectors help where false alarms are a problem. Spacing and siting are technical and belong to a competent designer — but knowing why a kitchen has a heat detector (not smoke) helps you spot when something's been fitted wrong.
Weekly: you or a nominated person test one manual call point, rotating so each is tested at least once a year. Monthly: a quick visual and standby-power check. Six-monthly (minimum): a service by a competent engineer, achieving full device coverage across the year. Logbook: record every test, service and fault — missing or incomplete logbooks are one of the most common failings fire officers find on inspection.
Take false alarms seriously
Too many false alarms and people stop believing the alarm — the "cry wolf" effect that gets people killed — and you drain fire-service resources. Investigate the cause promptly and fix it: re-site detectors away from steam and fumes, or switch to multi-sensor units.
The one thing to remember
The category must be justified by your fire risk assessment, and you must be able to show the records. A detection system that isn't tested and maintained is a system that fails at the only moment it matters. Learn where detection sits in the bigger picture in our fire warden guide.
Practise this in the game
The Alarm Panel drill puts you at the panel — fire or fault? — and asks for the right response under time pressure.
Play Hazard Hunt →This guide is for learning and applies to England & Wales. Always work from the current regulations, standards and your own fire risk assessment; Scotland and Northern Ireland have equivalent regimes.