BS 5839-6 is the British Standard code of practice for fire detection and fire alarm systems in domestic premises. It classifies a system by grade (the equipment and its power supply: A, C, D1, D2, F1 or F2) and category (how much of the dwelling is covered: LD1, LD2 or LD3). Building Regulations Approved Document B requires new dwellings in England to have at least a Grade D2 Category LD3 system, while BS 5839-6:2019 recommends Grade D1 LD2 for most new and rented homes. The installer issues a BS 5839-6 certificate for the alarm system and a separate BS 7671 certificate, an EIC or Minor Works Certificate, for the wiring that supplies it.
- Grade = the kind of system and how it is powered; category = the extent of coverage. Both are stated on the certificate, for example "Grade D1, LD2".
- Rented homes in England need at least one smoke alarm per storey and a CO alarm in rooms with a fixed combustion appliance under the 2015 Regulations as amended in 2022; BS 5839-6 goes further with Grade D1 LD2.
- Grade D alarms must be mains-powered with battery backup and interlinked so that all alarms sound together.
- BS 5839-6 has its own certificates for design, installation and commissioning; the electrical work is certified separately on an EIC or Minor Works Certificate.
- On an EICR the alarm circuit is tested but the alarm system is not assessed; note deficiencies as recommendations.
What is BS 5839-6 and who does it apply to?
BS 5839-6:2019+A1:2020 is the code of practice for fire detection and fire alarm systems in domestic premises: houses, flats, bungalows, houses in multiple occupation (HMOs), sheltered housing and similar. It is not law in itself, but it is the standard that Building Regulations guidance, landlord legislation, HMO licensing conditions and insurers all point to. Non-domestic buildings, including the common parts of blocks of flats, fall under BS 5839-1 instead.
What do the grades mean?
The grade describes the equipment and, most importantly, its power supply. The 2019 edition deleted the old Grades B and E and split D and F in two, based on whether the standby battery is tamper-proof.
| Grade | Description | Typical use |
|---|---|---|
| A | Full system to BS 5839-1: control panel, detectors, manual call points and sounders, with fire-resistant wiring | Large HMOs, sheltered housing, houses of four or more storeys |
| C | Detectors and sounders on a common power supply with central control equipment | Larger dwellings and some HMOs |
| D1 | Mains-powered smoke and heat alarms with an integral tamper-proof standby supply (sealed long-life battery) | New-build and rented dwellings; the current default |
| D2 | Mains-powered alarms with an integral replaceable standby battery | Older installations; still acceptable in many cases |
| F1 | Battery-powered alarms with a tamper-proof long-life battery | Existing owner-occupied dwellings where mains wiring is impractical |
| F2 | Battery-powered alarms with user-replaceable batteries | Lowest grade; not recommended for rented property |
Grade D always means mains-powered with battery backup: the alarm runs from the mains and the battery takes over during a power cut. An alarm with no backup, the old Grade E, is no longer recognised.
What do the categories mean?
The category describes how much of the dwelling has detection. Higher categories give earlier warning because fire is detected in the room of origin.
| Category | Coverage | Detectors |
|---|---|---|
| LD1 | All circulation spaces forming escape routes and all rooms and areas where fire may start, except bathrooms, shower rooms and toilets | Smoke alarms in circulation spaces, living rooms and bedrooms; heat alarm in the kitchen |
| LD2 | Circulation spaces plus rooms or areas that present a high fire risk to occupants, typically the living room and kitchen | Smoke alarms in hall and landing and living room; heat alarm in kitchen |
| LD3 | Circulation spaces forming the escape routes only | Smoke alarm in the hall and on each landing |
The grade and category are written together, so a typical new house is "Grade D1, LD2": mains alarms with sealed backup batteries in the hall, landing and living room, and a heat alarm in the kitchen, all interlinked.
What do new-build, rented and HMO homes typically need?
Three sets of rules overlap.
Building Regulations (new-build and material alterations)
Approved Document B Volume 1 for England requires all new dwellings to have a fire detection and alarm system of at least Grade D2 Category LD3 installed in accordance with BS 5839-6, with an interlinked smoke alarm in the circulation space on every storey and a heat alarm in any kitchen not separated from the circulation space by a door. Loft conversions and extensions that create a new storey trigger the same requirement across the whole house. BS 5839-6:2019 itself recommends Grade D1 LD2 for a new house, and many building control bodies expect that as the practical minimum, so specify D1 LD2 unless the client has a reason not to.
Rented property (Smoke and Carbon Monoxide Alarm Regulations)
The Smoke and Carbon Monoxide Alarm (England) Regulations 2015, as amended with effect from 1 October 2022, require private and social landlords in England to have at least one smoke alarm on every storey with a room used as living accommodation, a carbon monoxide alarm in any room with a fixed combustion appliance (gas cookers excluded), and to repair or replace an alarm as soon as reasonably practicable once told it is faulty. The Regulations do not specify grade or category, but government guidance points to BS 5839-6, and local authorities can fine up to £5,000 per breach. Wales requires mains-wired interlinked smoke alarms on each storey and CO alarms in rented homes under the Renting Homes (Wales) Act 2016, in force since December 2022. Scotland has required interlinked alarms in every home since February 2022: smoke alarms in the living room and every circulation space, a heat alarm in the kitchen and CO alarms where there is a fuel-burning appliance. Wider landlord duties are covered in EICR Landlord Requirements 2026: England, Scotland, Wales.
HMOs
For HMOs, BS 5839-6 and the LACORS housing fire safety guidance recommend a system based on size and layout. Small shared houses of up to three storeys are typically Grade D1 LD2, sometimes with an alarm in each bedroom. Larger HMOs, bedsits with cooking in rooms, and buildings of four or more storeys are typically Grade A LD2 in the common parts with Grade D alarms in the units. The licensing authority's conditions take precedence; check them before quoting.
| Dwelling type | Typical minimum recommended by BS 5839-6:2019 |
|---|---|
| New-build house or flat, up to 3 storeys | Grade D1, LD2 (ADB legal minimum: D2, LD3) |
| Existing owner-occupied house | Grade F1, LD2 |
| Existing rented house or flat, up to 3 storeys | Grade D1, LD2 |
| Small HMO (shared house, up to 3 storeys) | Grade D1, LD2 |
| Large HMO or 4+ storeys | Grade A, LD2 in common parts, plus Grade D in units |
These are typical figures; check the current edition's table and the licensing conditions for the actual property.
What does BS 5839-6 require of the installation?
The recommendations most relevant to the electrician are:
- Power supply. Grade D alarms may be fed from a dedicated circuit or from a regularly used local lighting circuit, the latter because a supply failure would be noticed quickly. Label the circuit at the board. BS 5839-6 advises against RCD protection of the alarm circuit unless BS 7671 requires it, and then an RCBO serving only that circuit is preferred so a fault elsewhere does not disconnect the alarms.
- Interlinking. All alarms in a Grade D system must be interconnected so that every alarm sounds when one is triggered, by a third core or by radio link.
- Siting. Smoke alarms on the ceiling, at least 300 mm from walls and light fittings, within 3 m of every bedroom door, and not in kitchens or bathrooms; heat alarms in kitchens.
- Standby supply. Grade D1 alarms have a sealed battery designed to last the life of the alarm, commonly 10 years, and carry a replace-by date.
- Wiring. Ordinary PVC cable is acceptable for Grade D; fire-resistant cable is required for Grade A and some Grade C systems.
What certificates does BS 5839-6 require?
BS 5839-6 includes model certificates in its annexes. For Grade A and C systems there are separate design, installation and commissioning certificates mirroring BS 5839-1. For Grade D and F systems, where one contractor usually does everything, there is a simpler combined certificate of design, installation and commissioning recording the grade and category, the number and location of alarms, the interlinking method, and confirmation that each alarm was tested and the occupier shown how to test them.
The certificate should also record any variations from the standard, such as an LD3 system fitted where the landlord declined LD2, so that the decision and responsibility are documented. Commissioning a Grade D system means testing every alarm with the test button, confirming the interlink causes all alarms to sound, checking the mains indicator on each unit, and isolating the circuit briefly to prove the standby supply. Record the date and hand the occupier the manufacturer's instructions.
How does a smoke alarm installation interact with the EIC and EICR?
Mains-powered alarms are part of the fixed electrical installation, so BS 7671 certification applies alongside the BS 5839-6 certificate.
| Work | BS 7671 certificate | BS 5839-6 certificate |
|---|---|---|
| New dedicated alarm circuit from the consumer unit | EIC | Design, installation and commissioning |
| Alarms added to an existing lighting circuit | Minor Works Certificate | Design, installation and commissioning |
| Alarms fitted as part of a rewire | Included on the rewire EIC | Design, installation and commissioning |
| Periodic inspection | EICR covers the circuit only | Not covered; recommend BS 5839-6 inspection |
When to use each BS 7671 form is explained in Minor Works Certificate: When to Use It (and When Not To) and Electrical Installation Certificate (EIC) Explained. In England and Wales a new alarm circuit in a dwelling is also notifiable under Part P (/guides/part-p-notification-explained); adding alarms to an existing circuit is not, unless in a special location.
On an EICR (Electrical Installation Condition Report) the inspector tests the alarm circuit like any other: insulation resistance with line and neutral linked so the alarm electronics are not stressed, polarity, earth fault loop impedance and, where fitted, RCD operation (/guides/how-to-do-an-eicr-step-by-step). The inspector does not verify the alarm system against BS 5839-6, because that standard is outside the scope of BS 7671, and Electrical Safety First's Best Practice Guide 4 advises that the absence of smoke alarms is not coded on an EICR. What the inspector should do is note what was seen ("mains smoke alarms present in hall and landing, no heat alarm in kitchen, alarms not verified to BS 5839-6") in the comments and recommend a BS 5839-6 inspection where the system looks inadequate; how comments and limitations are worded is covered in EICR Sampling and Limitations Explained: Extent, LIM and N/V. Where the circuit is defective in BS 7671 terms, for example an interconnect cable with exposed conductors, it is coded in the normal way as set out in EICR Codes Explained: C1, C2, C3 and FI (with examples).
How Certio helps
Certio produces the EICR, EIC, Minor Works certificate and PAT records on the BS 7671 model forms and turns them into branded PDFs. Photograph the consumer unit and the circuit schedule drafts itself; point the phone camera at a Megger MFT-X1 and the reading goes straight into the schedule of test results, or dictate it while your hands stay on the probes. Suggested observation wording with the regulation reference is there for you to check and confirm. The judgement stays yours; the typing goes. Starter is free for 7 days, then £5 a month.