Fire alarm systems, explained and installed to BS 5839.

A fire alarm system detects a fire early and warns everyone in the building in time to get out. Detectors watch for smoke or heat, the panel works out where the signal came from, and sounders and beacons tell people to leave. Call points by the exits let anyone raise the alarm by hand.

What the panel does next is the cause and effect: which sounders ring, which doors release, which vents open. It is mapped out for each building, not left as one generic response.

Addressable or conventional

Addressable systems report the exact device, so you know it is the detector outside flat 14, not just the third floor. Conventional systems report by zone. They cost less and suit smaller, simpler buildings. Wireless panels use radio-linked detectors where running new cable is impractical, such as listed buildings.

The equipment

Control panels	Addressable, conventional or wireless, sized to the building.
Optical smoke detectors	General coverage for most rooms and corridors.
Heat detectors	Kitchens and plant rooms, where steam or fumes would trip a smoke detector.
Multi-sensors	Smoke and heat in one head, fewer false alarms.
Aspirating detection	Sampling pipes for very early warning in server rooms and high-value storage.
Manual call points	Break-glass units by exits and on escape routes.
Sounders, beacons and VADs	Audible and visual warning, including for people who are deaf or hard of hearing.
Interfaces	AOV vents, door holders, mag locks, sprinklers and air handling plant, all released on the alarm signal.
Repeater panels	Alarm status at the entrance or security desk.
Remote signalling	Wired ready for an alarm receiving centre (ARC), and we can put you in touch with a monitoring provider.

BS 5839 and the categories

BS 5839-1 covers non-domestic buildings, including the communal areas of larger residential blocks. BS 5839-6 covers dwellings and HMOs. Part 1 sets a category by what the system protects and how much of the building it covers.

Category	Coverage
L1	Life safety, detection in virtually every room.
L2	Escape routes plus specific higher-risk areas.
L3 and L4	Escape routes, corridors and stairs.
L5	Bespoke, for a localised risk named in the fire risk assessment.
P1 and P2	Property protection, the whole building or specific high-risk rooms.
M	Manual call points only, no automatic detection.

Most buildings combine them, often L2 or L3 with P2 for high-value rooms. The fire risk assessment sets the category, so we survey before we quote.

BAFE accredited

BAFE is the independent accreditation scheme for fire alarm contractors in the UK. An outside body audits our design, installation, commissioning and maintenance work on an ongoing basis, so your fire risk assessor, building control or insurer does not have to take our word for it.

Testing, servicing and the log book

Weekly	Test a different call point, done by a responsible person on site.
Every six months	Full service by a competent contractor: detectors, panel, wiring and batteries.
Every visit	Tests, faults and remedial work recorded in the log book kept on site.

A gap in the log is treated the same as a missed test. We run the schedule and keep the log current under weekly testing and planned servicing.

Blocks of flats since Grenfell

The Fire Safety Act 2021 brought external walls and flat entrance doors into scope, and the Building Safety Act 2022 added duties for higher-risk buildings. Many blocks are replacing a waking watch with a permanent common-parts alarm, which usually lets the waking watch stand down at a fraction of the ongoing cost.

What we do

We survey, specify, install, commission and maintain, all in-house, so one team stays accountable from design to every service visit. For an existing system with no clear history, we run a takeover survey and bring it up to BS 5839 before it moves onto a maintenance contract.

We work in offices, apartment blocks, HMOs, schools, industrial units and mixed-use buildings, and we commission fire alarms alongside AOV smoke ventilation and door entry and access control as one coordinated scheme.