BS 5839-6:2019+A1:2020 is the current code of practice for fire detection and fire alarm systems in domestic premises. It describes a system by grade (the equipment and its power supply: A, C, D1, D2, F1 or F2) and by category (how much of the dwelling is covered: LD1, LD2 or LD3). Its Table 1 recommends Grade D1, Category LD2 for rented homes of up to three storeys. When you install mains alarms you issue two documents: the BS 5839-6 certificate of design, installation and commissioning, modelled in Annex E for Grade C, D and F systems, and a BS 7671 certificate for the wiring, which is an Electrical Installation Certificate or a Minor Works certificate.
- The current edition is BS 5839-6:2019+A1:2020. BSI lists it as current, with Amendment 1 published on 31 October 2020.
- Grade is the kit and its power supply. Category is the coverage. Both go on the certificate, for example "Grade D1, Category LD2".
- Table 1 asks for more than the law. Approved Document B accepts Grade D2, LD3 in a new dwelling, while Table 1 recommends LD2.
- Where an existing owner-occupied home is rewired, Table 1 calls for a Grade D, LD2 system, so a rewire quote should include mains interlinked alarms.
- Annex E is the model certificate for Grade C, D and F systems. Annex D covers Grade A, and Annex H is the inspection and servicing certificate.
- An EICR tests the alarm circuit. It does not verify the alarm system against BS 5839-6.
Which edition of BS 5839-6 is current?
BS 5839-6:2019+A1:2020. The 2019 revision took effect on 30 April 2019 and replaced the 2013 edition. Its foreword lists the main changes: Grades B and E were removed, Grades D and F were each split in two, Table 1 was revised, a new Table 3 set out testing and servicing by grade, and the standard of protection in sheltered housing flats rose from LD2 to LD1. Amendment 1, published on 31 October 2020, added a warning that children might not be woken by fire alarm tones.
One thing has moved since. BS 5839-1, the non-domestic code that Grade A systems are built to, was reissued as BS 5839-1:2025 with effect from 30 April 2025, when the 2017 edition was withdrawn. The IET's Wiring Matters confirms the 2025 edition still covers the design, installation and commissioning of Grade A systems that conform to BS 5839-6. If you only fit Grade D alarms, nothing changes for you.
BS 5839-6 is a code of practice, not law. It matters because Building Regulations guidance, landlord legislation, HMO licensing conditions and insurers all point to it.
What do the grades mean?
The grade tells you what the equipment is and how it is powered. The D and F splits turn on whether the battery can be removed.
| Grade | What it is | Where you meet it |
|---|---|---|
| A | Separate detectors, sounders and control and indicating equipment with a back-up supply, built to BS 5839-1 with BS EN 54 equipment | Large houses, bigger HMOs, sheltered housing communal areas |
| C | Detectors and sounders on a common mains supply with standby, plus central control equipment | Larger dwellings, some HMOs |
| D1 | Mains-powered alarms, each with a tamper-proof standby battery | Rented homes; the usual choice for new work |
| D2 | Mains-powered alarms, each with a user-replaceable standby battery | New owner-occupied homes as a minimum |
| F1 | Battery-only alarms with a tamper-proof battery | Existing owner-occupied homes where battery changes are in doubt |
| F2 | Battery-only alarms with a user-replaceable battery | Existing owner-occupied homes only |
A tamper-proof battery is one not designed to be removed, such as cells soldered to the board. The price gap between D1 and D2 alarms is small, and D1 satisfies every row of Table 1 that asks for D2, so many electricians fit D1 as standard.
What do the categories mean?
The category is the extent of detection. Higher categories give earlier warning because the fire is detected in the room where it starts.
| Category | Coverage | In practice |
|---|---|---|
| LD1 | All circulation spaces that form escape routes, and all rooms and areas where a fire might start, other than bathrooms, shower rooms and toilets | Smoke alarms in halls, landings, living rooms and bedrooms; heat alarm in the kitchen |
| LD2 | Circulation spaces plus rooms and areas that present a high fire risk | Smoke alarms in hall, landings and the principal habitable room; heat alarm in every kitchen |
| LD3 | Circulation spaces that form escape routes only | Smoke alarms in the hall and on each landing |
Note D to Table 1 fixes what LD2 means in a typical house: heat detectors in every kitchen and a smoke detector in the principal habitable room, or in each room that could be used as one.
What does Table 1 recommend for each type of home?
Table 1 gives a minimum grade and category for each class of premises, in two columns: new or materially altered, and existing. The rows below are for dwellings with no floor over 200 m².
| Premises | New or materially altered | Existing |
|---|---|---|
| Rented flat, bungalow or house, up to three storeys | D1, LD2 | D1, LD2 |
| Owner-occupied flat, bungalow or two-storey house | D2, LD2 | F2, LD3 |
| Owner-occupied three-storey house | D2, LD2 | F2, LD2 |
| Owner-occupied house, four or more storeys | A, LD2 | D2, LD2 |
| Rented house, four or more storeys | A, LD1 | D1, LD1 |
| HMO of one or two storeys | D1, LD1 | D1, LD2 |
| Larger HMO | D1 in the units (LD1 in bedsits, LD2 in units of two or more rooms); Grade A, LD2 in communal areas | The same |
| Sheltered housing flats | D2, LD1 | D2, LD2 |
| Self-catering and short-term lets | D1, LD1 | D1, LD1 |
Three notes to the table are worth knowing on site:
- Note F. Where electrical work such as a rewire is carried out in an existing owner-occupied home, a Grade D, Category LD2 system should be installed. Battery alarms stop being acceptable the moment the floors are up.
- Note E. Grade F1 is advised over F2 wherever there is doubt about batteries being replaced.
- Note G. In Scotland, Grade F1, LD2 is the minimum in every existing dwelling.
Maisonettes with a floor more than 4.5 m above ground and dwellings with a floor over 200 m² have their own rows, mostly Grade A or LD1. Table 1 assumes the occupants are unknown. A fire risk assessment can justify more than the table, never less. Check the table and its notes for the actual property before you quote.
What do Building Regulations and landlord law require?
Less than Table 1, in most cases.
New dwellings and alterations. Approved Document B Volume 1 says all new dwellings in England should have a system of at least Grade D2, Category LD3 to BS 5839-6, and GOV.UK's Approved Document B FAQ confirms that this lower figure still satisfies Part B even though Table 1 recommends more. A heat alarm is added where the kitchen is not separated from the circulation space by a door. A large dwellinghouse, meaning one with a storey over 200 m², needs Grade A: LD3 for two storeys, LD2 for three or more. Where an extension or loft conversion adds habitable rooms above or below the ground storey, or a ground-storey room with no final exit, smoke alarms go in the circulation spaces of the house. Building control often expects LD2 in practice, so ask before first fix.
Rented homes. The Smoke and Carbon Monoxide Alarm (England) Regulations 2015, as amended from 1 October 2022, require at least one smoke alarm on every storey used as living accommodation and a carbon monoxide alarm in any room with a fixed combustion appliance other than a gas cooker. They do not set a grade. The penalty is up to £5,000. Wales has required a mains-connected, interlinked smoke alarm on every storey of rented homes since 1 December 2022. Scotland has required interlinked alarms in every home since February 2022. The electrical side of landlord duties is in our guides to landlord EICR regulations in England and Scotland and Wales.
HMOs. The licensing authority's conditions decide, usually drawing on Table 1 and the LACORS housing fire safety guide. Get the conditions in writing before pricing. Our EICR for HMOs guide covers the inspection side.
How should a Grade D system be wired and sited?
Supply. Clause 15.4 gives two options for Grade D: an independent circuit from the dwelling's consumer unit, or a regularly used local lighting circuit. The lighting circuit is allowed because a lost supply gets noticed the same evening. Label the protective device either way.
RCD protection. In practice the alarm circuit will be RCD protected, because BS 7671 leaves little choice: Regulation 411.3.4 requires 30 mA RCD protection for lighting circuits in domestic premises, and cables buried less than 50 mm deep in walls usually need it under Regulation 522.6.202. The tidy answer is an RCBO serving only that circuit, so a fault on the sockets or the shower cannot take the alarm supply out. The standby battery covers a trip, but it should not be doing so for weeks unnoticed. Board choice is covered in RCBO vs RCD split-load boards.
Interlinking. Every alarm must sound when one operates. Hard-wired interlinked alarms belong on a single final circuit, so that one isolation makes the whole system dead. If the alarms have to be fed from different circuits, use radio interlink. Clause 16.4 asks for the interlink conductor to be readily distinguishable from the power conductors, so sleeve it and do not leave it brown.
Siting. Clause 11.2 has the detail. The figures that catch people out:
- Ceiling-mounted, at least 300 mm from walls and light fittings.
- A smoke alarm within 3 m of every bedroom door.
- No point in a circulation space or protected room more than 7.5 m from the nearest smoke alarm, or 5.3 m from the nearest heat alarm.
- On a pitched ceiling, smoke alarms within 600 mm of the apex measured vertically, heat alarms within 150 mm.
- No smoke alarms in kitchens or bathrooms. Kitchens get a heat alarm.
Cable. Ordinary thermoplastic twin and earth and three-core and earth are acceptable for Grade D. Grade A needs fire-resistant cable to BS 5839-1. Regulation 521.10.202 on support against premature collapse applies to all of it.
What certificates does BS 5839-6 call for?
Clause 23.3 recommends a certificate on completion, and the annexes give model forms.
| Document | Annex | When |
|---|---|---|
| Design, installation and commissioning certificates, Grade A | Annex D | New Grade A system; separate signatures for each stage |
| Design, installation and commissioning certificate, Grade C, D and F | Annex E | Every new Grade C, D or F system and every extension or alteration |
| Guidance to occupiers and landlords | Annex F | Handed over with the user instructions that clause 24 asks for |
| Inspection and servicing certificate | Annex H | After any periodic service |
The Annex E form records the address, the grade and category, the areas protected for an LD2 system, any variations from the standard, and a declaration that the system was tested and the user instructions handed over. NICEIC and the main alarm manufacturers publish versions of it. If you did the design, installation and commissioning yourself, you sign for all three. If someone else specified the system, delete the words that do not apply and sign for your part only.
Two points matter when filling it in. Record variations honestly. An LD3 system fitted because the landlord declined LD2 is a variation, and writing it down puts the decision where it belongs. And be clear how you tested. Clause 23.3 expects each detector to be functionally tested, smoke alarms with a method that gets smoke or test aerosol into the chamber and heat alarms with a heat source. Where the manufacturer's own procedure was followed instead, the manufacturers' forms have a line to say so.
Which BS 7671 certificate goes with it?
Mains alarms are part of the fixed installation. BS 7671 points to the BS 5839 series for fire detection and alarm systems (Regulation 560.10), but the circuit itself is certified like any other.
| Work | BS 7671 certificate | BS 5839-6 certificate |
|---|---|---|
| New dedicated alarm circuit | EIC | Annex E |
| Alarms added to an existing lighting circuit | Minor Works | Annex E |
| Alarms fitted during a rewire | On the rewire EIC | Annex E |
See when to use a Minor Works certificate and the EIC explained. A new circuit in a dwelling is notifiable under Part P. For insulation resistance, unplug the alarm heads from their bases first. Where that is not practicable, Regulation 643.3 of BS 7671 allows the test voltage to be reduced to 250 V d.c., provided the reading is still at least 1 MΩ. Our insulation resistance testing guide has the method.
What testing and servicing does Table 3 expect?
Table 3 was new in 2019. Tell the client what it says at handover.
| Grade | Occupier's test | Servicing by a competent person |
|---|---|---|
| A | Weekly | At intervals of no more than 6 months, to BS 5839-1 |
| C | Monthly, at the central control equipment | Every 12 months in sheltered and telecare schemes; otherwise to the manufacturer's instructions |
| D and F | Monthly, using the test button | Every 12 months in sheltered and telecare schemes; otherwise none specified |
Batteries in Grade D and F alarms are replaced to the manufacturer's instructions or at the low-battery warning, whichever comes first. Most alarms carry a replace-by date, commonly ten years from manufacture.
Are smoke alarms checked on an EICR?
The circuit is. The system is not. On an Electrical Installation Condition Report you inspect and test the alarm circuit like any other: insulation resistance, polarity, earth fault loop impedance and RCD operation. You do not verify the alarm system against BS 5839-6. BS 7671 does not require a dwelling to have smoke alarms, so there is no regulation to cite for their absence and no basis for a classification code.
What you should do is record what you saw. A note such as "Mains smoke alarms in hall and landing, no heat alarm in kitchen, alarm system not verified to BS 5839-6, recommend review" tells the landlord something useful without claiming an inspection you did not carry out. State in the extent and limitations that the fire alarm system is outside the report, as covered in EICR sampling and limitations. Defects in the wiring itself, such as an interlink cable with exposed conductors or no CPC at an alarm base, are coded in the normal way using C1, C2, C3 and FI.
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 £4.99 a month.