Fire Alarm Installation

Getting the category right

Every system installed under BS 5839-1 is given a category — a letter-and-number code describing what it protects and how much of the building it covers. Getting this right is the difference between a proportionate, compliant system and one that is either wildly over-specified or dangerously thin. The category should follow from your fire risk assessment.

Category M — manual systems

Manual call points only, with no automatic detection. The people in the building are the detectors. Suitable only where the premises are fully occupied whenever detection is needed. Low cost and very reliable, but a fire starting in an unoccupied part of the building can grow undetected.

Category L — life protection

• L1 — detection throughout all areas, including roof voids, cupboards, plant rooms and service areas. The highest level of protection, typically specified for care homes and buildings where occupants sleep or need help to evacuate.
• L2 — as L3, plus detection in defined high-risk rooms such as kitchens, plant rooms or stores. Common in hotels and larger commercial premises.
• L3 — detection in escape routes and in rooms opening onto them, so a fire next to an exit route is caught before it blocks the escape. A sound default for most workplaces.
• L4 — detection in the escape routes themselves: corridors and stairways. Basic escape-route warning only.
• L5 — the custom category, designed around a specific fire-safety objective identified by a risk assessment. Often used alongside another category.

Category P — property protection

P1 covers the whole building with detection; P2 covers defined high-risk areas only, such as a server room or archive. Property categories are usually driven by an insurer's requirements rather than by law.

An important 2025 change

The 2025 revision of BS 5839-1 makes clear that rooms where people sleep should have smoke detection rather than heat detection. If your building has any sleeping accommodation, heat detectors alone are no longer acceptable — this particularly affects L2 and L3 designs.

System types we install

• Addressable — each device reports its own location to the panel, so faults and alarms are pinpointed instantly. Best for anything but the smallest buildings.
• Conventional — devices grouped into zones. Cost-effective for small, simple premises.
• Wireless — ideal for listed buildings, occupied premises and anywhere cabling would be disruptive.

What we deliver

Design to the agreed category, installation, full commissioning including cause-and-effect programming, zone plans, and a handover pack with the certification you need for building control, insurers and your fire risk assessor.