Category M — manual systems
Manual call points and sounders only, with no automatic detection. Suitable where occupants are awake, alert and able to raise the alarm themselves, and where escape routes are short and simple — a small shop or a single-storey office, for example.
Category L — protection of life
L systems add automatic detection. The number tells you how much of the building is covered:
- L1 — detection throughout all areas of the building. The earliest possible warning; used in care homes, hospitals and high-risk sleeping accommodation
- L2 — as L3, plus detection in defined high-risk rooms such as kitchens, plant rooms or storage
- L3 — detection in escape routes and in all rooms opening onto them, giving warning before escape routes become impassable
- L4 — detection in escape routes only
- L5 — an engineered category designed to satisfy a specific fire safety objective identified in the risk assessment
Category P — protection of property
P systems exist to summon the fire service early enough to limit damage, usually at an insurer's request. P1 covers all areas of the building; P2 covers defined high-risk areas only. A building often needs both an L and a P element, in which case the higher requirement applies in each area.
Zones, cause and effect, and false alarms
BS 5839-1 sets out how a building is divided into zones so that the panel tells responders where the fire is — generally no more than 2,000 square metres per zone, no zone spanning more than one storey except in small buildings, and search distances kept short.
The standard also gives a false alarm rate target of no more than one per 100 detectors per year. Where a system exceeds that, the cause must be investigated: poor detector siting near kitchens or showers, the wrong detector type, contamination, or missing filtering are the usual culprits.
Testing and servicing requirements
The standard's maintenance regime is the part that shows up in enforcement. Weekly user testing of a different call point each week, recorded in the logbook. Periodic inspection and servicing by a competent person at intervals not exceeding six months, with every device tested at least annually.
Systems should also have a documented design certificate, installation certificate and commissioning certificate. If those are missing from a legacy system, a verification survey against BS 5839-1 is the way to establish a baseline.
Need help meeting these requirements?
Lumacore Group carries out fire risk assessments, fire alarm design and maintenance, fire door surveys and emergency lighting testing across Newcastle and the North East, with full digital compliance records.