BS 5839 explained.
The British Standard behind most fire alarm design and servicing, without the jargon.
What it is
BS 5839 is the British Standard covering fire detection and alarm systems for buildings. It is a code of practice: it recommends how systems should be designed, installed, commissioned and maintained. Part 1 covers non-domestic premises; Part 6 covers homes.
BS 5839-1: non-domestic premises
Part 1 describes categories of system:
| Category | What it means | Typical use |
|---|---|---|
| L1 | Detection throughout the building | Highest life protection, such as sleeping accommodation |
| L2 | Detection on escape routes and in high-risk rooms | Higher life protection in some buildings |
| L3 | Detection on escape routes and rooms opening onto them | Common life-safety standard |
| L4 | Detection on escape routes only | Limited life protection |
| L5 | Detection designed for a specific purpose | Particular risk, set by a designer |
| M | Manual call points only | Where there is no automatic detection |
| P1 / P2 | Property protection: throughout or in defined areas | Protecting the building and contents |
The category is not chosen by the installer alone: it comes from the fire risk assessment and, where relevant, from insurers or the enforcing authority.
BS 5839-6: homes
Part 6 sets grades of equipment (for example Grade D: mains-powered alarms with a standby battery) and categories of coverage LD1 to LD3, from detection in all rooms down to escape routes and the room of highest risk. See domestic fire alarms.
Maintenance and records
The standard recommends servicing at intervals of not more than six months, a logbook and a competent person responsible for the system. See servicing and maintenance.
Why it matters
- Insurers and enforcing authorities commonly look for compliance with it
- It sets how many detectors, where and of what type
- It tells you what paperwork to expect when a system is installed
A code of practice, not a lawBS 5839 is a recognised standard. The law is the Regulatory Reform (Fire Safety) Order 2005, and the standard is the usual way of showing a system is adequate. See your responsibilities.
Standards are revised from time to time. Always work from the current edition.
Common questions.
What is BS 5839-1?
The code of practice for fire detection and alarm systems in non-domestic premises, covering design, installation, commissioning and maintenance.
What do L1, L2 and L3 mean?
They are categories of automatic life-protection systems. L1 covers the whole building, L2 escape routes and high-risk rooms, and L3 escape routes and rooms opening onto them.
Is BS 5839 a legal requirement?
It is a code of practice, not a law, but it is the usual way to show a system is adequate to meet the duties under fire safety legislation.
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