When you ask for a fire alarm system, two British Standards come up repeatedly: BS 5839-1 and BS 5839-6. They look similar, but they apply to different kinds of premises and are not interchangeable.
BS 5839-1: non-domestic premises
BS 5839-1 is the code of practice for the design, installation, commissioning and maintenance of fire detection and fire alarm systems in non-domestic premises. The current edition is BS 5839-1:2025, which replaced the 2017 edition. According to BSI, the 2025 revision adds a section on modifying existing systems, restricts certain variations from the standard, simplifies manual call point guidance and gives stronger preference to automatic detection in sleeping areas. That includes offices, shops, warehouses, factories, schools, community buildings and other commercial or public buildings.
It describes system categories according to the purpose of the system:
- L categories are systems intended to protect life. They range from systems covering only escape routes to systems covering the whole building.
- P categories are systems intended to protect property.
- Category M is a manual system, where people raise the alarm using manual call points but there is no automatic detection.
The category is not chosen from a menu. It follows from the building's fire strategy and fire risk assessment, and is sometimes dictated by an insurer, a regulator or a licence condition.
BS 5839-6: domestic premises
BS 5839-6 (current edition BS 5839-6:2019+A1:2020) is the code of practice for fire detection and fire alarm systems in domestic premises, such as houses and individual dwellings. It uses a different structure from BS 5839-1: grades (which describe the type of equipment and power supply) and categories (which describe how much of the home is covered).
In England, separate regulations require landlords of private rented homes to provide smoke alarms and, in some cases, carbon monoxide alarms. Those duties are not the same thing as a BS 5839-6 system and the detail is outside the scope of this article. Take advice if you let property.
Why neither standard covers every residential setting
Residential buildings are not all the same. A single private house is a domestic premises. A purpose-built block of flats has individual flats and communal areas, and the fire strategy for the building determines how they are protected. A house in multiple occupation (HMO) may have additional requirements set by the local authority licence. Sheltered housing, care homes and holiday lets each have their own considerations.
So we do not say that one standard, or one certification scope, covers every residential setting. For anything other than a single dwelling, the starting point is the fire strategy and risk assessment, and the standard that applies to each part of the building follows from that.
Domestic and HMO systems at Omni3
We also design and install fire detection and alarm systems for domestic premises and houses in multiple occupation (HMOs), working to BS 5839-6 where it applies. The applicable standard depends on the premises and the system. Not every HMO falls solely under BS 5839-6: larger or more complex buildings, communal areas and mixed-use buildings may need to be considered under BS 5839-1 or other guidance, together with the fire risk assessment and any licence conditions. For the work we undertake, we provide the appropriate certificates, reports and supporting documentation for our scope of responsibility.
What to ask a designer
- Which standard are you designing to, and why does it apply to this building?
- Which category of system are you proposing, and what is it based on?
- What assumptions are you making about use and occupancy, and who has confirmed them?
- Which parts of the system are not covered?
For more on how design works, read how a commercial fire alarm system is designed. For HMOs, see our HMO electrical and fire systems page.
Related service: Fire Alarm Design