Life-safety systems
Smoke, heat & CO alarms
The alarm system fitted to a dwelling is graded under BS 5839-6. For a typical new dwelling in England, Approved Document B describes a minimum Grade D2 LD3system — mains-powered alarms with battery back-up covering escape routes. The design may need a higher grade or wider coverage after assessing the property and its occupants.
Grade & category — what the letters mean
Grade D
Mains-powered alarms with integral standby batteries. Grade D1 has a tamper-proof battery; Grade D2 has a user-replaceable one.
Category LD2
Detection in escape routes (halls, landings) and in rooms presenting a high fire risk (typically the living room / lounge, plus a heat alarm in the kitchen).
Typical Grade D LD2 layout
- Hall / landing on every storey: optical smoke alarm.
- Living room / principal habitable room: optical smoke alarm.
- Kitchen: heat alarm (not smoke — cooking causes nuisance alarms).
- All units interlinked — wired or wireless — so any alarm sets off every alarm.
- Grade D alarms can be supplied from a separately protected, regularly used local lighting circuit or an independent circuit; each alarm has its own standby battery.
Carbon monoxide alarms
English rental law (Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022) requires landlords to fit a CO alarm in everyroom used as living accommodation that contains a fixed combustion appliance (excluding gas cookers). Alarms should meet BS EN 50291-1 and be sited to manufacturer's instructions — typically at head height and within 1–3 m of the appliance.
England, Wales, Scotland — key differences
- Scotland requires Grade D LD2 in every home (not just rentals) since February 2022 — the tightest regime in the UK.
- England: Approved Document B gives Grade D2 LD3 as the normal minimum for new dwellings; rented-property alarm duties differ from new-build guidance and should be checked separately.
- CO alarms: in England and Wales the legal duty applies to rented accommodation (rooms with a fixed combustion appliance, excluding gas cookers in England). Scotland requires CO alarms in every home with a combustion appliance. For owner-occupied homes in England and Wales a CO alarm is strongly recommended rather than legally required.