Fire alarms

A Part 1 fire detection and alarm system is a building-wide system designed in line with BS 5839-1 for non-domestic premises such as offices, schools, hospitals and large residential blocks. It uses a combination of automatic fire detectors and manual call points to give early warning of fire throughout the building, so people can be alerted quickly, escape safely and damage to the property can be reduced.

Part 1

What types of fire systems are there?

Part 6

A Part 6 fire detection and alarm system is designed for domestic premises, such as houses, flats and small HMOs, in line with BS 5839-6. It uses mains-powered or battery-powered smoke and heat alarms, often interlinked, to give early warning of fire in key areas like escape routes, living rooms, bedrooms and kitchens, helping people wake up, escape safely and reduce fire damage.

But What Are The Grades And Categories?

Categories of Part 1 systems (BS 5839‑1)

Category L – Life protection

These systems are mainly about protecting people.

L1 – Automatic fire detection is installed throughout all areas of the building. This gives the earliest possible warning of fire anywhere on the premises. It is usually used in high‑risk or sleeping‑risk buildings such as hotels, care homes, student accommodation and hospitals.

L2 – Automatic detection is installed in escape routes (corridors, stairwells) and in specified high‑risk rooms or areas (for example plant rooms, kitchens, boiler rooms or areas with high fire load). This is used where there is a higher fire risk in certain areas and early warning is needed to protect escape routes.

L3 – Automatic detection is installed in escape routes and in all rooms that open directly onto those escape routes. The aim is to give early warning so that people can escape before corridors and stairs become smoke‑logged.

L4 – Automatic detection is installed only in escape routes such as corridors and stairways. This provides warning of fire affecting escape routes but does not give early warning of a fire starting in rooms away from those routes.

L5 – A custom or “engineered” system designed to meet a specific fire safety objective. Detection is installed only in defined areas where a particular risk has been identified, for example to protect a specific high‑risk process or piece of equipment.

Category M – Manual systems

M – A manual fire alarm system with call points (break‑glass units) and sounders only, with no automatic fire detection. Occupants raise the alarm by operating a call point when they discover a fire. These systems rely on people being present and able to spot a fire quickly.

Category P – Property protection

These systems are mainly about protecting the building and its contents, and limiting business interruption.

P1 – Automatic fire detection is installed throughout all areas of the building to provide the earliest possible warning of fire anywhere on the premises. The aim is to reduce damage to the building and contents and to support business continuity.

P2 – Automatic detection is installed only in defined high‑risk areas where a fire is most likely to start or where damage would be most serious, such as plant rooms, server rooms or storage areas with high fire load.

Grades of system (overview)

You will often hear references to “grades” of system, especially in domestic or HMO settings. These are mainly defined in BS 5839‑6 (for domestic premises) and describe the type and reliability of the equipment and power supplies used.

Common grades include:

Grade A – A full fire alarm system with a control and indicating panel, separate detectors, call points and sounders, with mains power and standby batteries. This is similar in concept to a Part 1 system but applied in domestic or HMO environments.

Grade C – A system of fire detectors and sounders (or combined units) connected to a common power supply with central control and standby supply.

Grade D1 / D2 – Mains‑powered smoke or heat alarms with integral standby batteries.

D1 – With a tamper‑proof (non‑replaceable) battery.

D2 – With a user‑replaceable battery.

Grade F1 / F2 – Battery‑powered smoke or heat alarms only.

F1 – With a tamper‑proof (non‑replaceable) battery.

F2 – With a user‑replaceable battery.

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Wistonia electrical & security will design, install and commission all types of fire detection and alarm systems, providing all BS 5839-1 required documentation on completion. Before any fire system is designed, we always recommend that a suitable and sufficient fire risk assessment is carried out first, so the system can be tailored to the specific risks and layout of your building.