BS 5839-6 is the British Standard code of practice for fire detection and fire alarm systems in domestic premises such as houses, flats, houses in multiple occupation (HMOs) and sheltered housing. It describes a system in two ways. The Grade (A, C, D1, D2, F1 or F2) sets how the system is built and powered. The Category (LD1, LD2 or LD3 for life safety) sets how much of the home it covers. The current edition is BS 5839-6:2019+A1:2020.
This guide explains each fire alarm grade and category, what changed in 2019, and how the standard's minimum recommendations work in practice.
What is BS 5839-6?
BS 5839 is a multi-part standard. Part 1 covers fire detection and fire alarm systems in non-domestic premises (see our guide to BS 5839-1 categories). Part 6 covers dwellings. Part 6 is a code of practice: it makes recommendations for the design, installation, commissioning and maintenance of domestic systems. Designers, installers, landlords and enforcing authorities widely use it as the benchmark for "suitable" smoke and heat detection in the home.
The 2019 edition was a significant revision, and Amendment 1 followed in 2020. If you are specifying or replacing alarms, work to the current edition rather than older guidance based on the 2013 text.
Fire alarm grades explained
The grade describes the type of equipment and, above all, how it is powered. Grade A is the most comprehensive and F2 the most basic.
| Grade | What it means |
|---|---|
| Grade A | Separate detectors and sounders with control and indicating equipment and power supply equipment conforming to BS EN 54-2 and BS EN 54-4, similar to a commercial fire alarm panel system. |
| Grade C | Fire detectors and alarm sounders (which may be combined as smoke alarms) connected to a common power supply, made up of the normal mains and a standby supply, with central control equipment. |
| Grade D1 | One or more mains-powered detectors, each with a tamper-proof standby supply consisting of a battery or batteries. |
| Grade D2 | One or more mains-powered detectors, each with an integral standby supply consisting of a user-replaceable battery or batteries. |
| Grade F1 | One or more battery-powered detectors powered by a tamper-proof primary battery or batteries. |
| Grade F2 | One or more battery-powered detectors powered by a user-replaceable primary battery or batteries. |
What changed in the 2019 revision?
BS 5839-6:2019 simplified and tightened the grading system:
- Grades B and E were removed.
- Grade D was split into D1 and D2, and Grade F into F1 and F2, to separate alarms with tamper-proof batteries from alarms with user-replaceable batteries.
- The table of minimum recommendations was updated. LD2 became the typical minimum category for many new and materially altered homes.
Amendment 1:2020 added a warning that children might not be woken by typical fire alarm tones. Household escape plans should take this into account.
What is a Grade D fire alarm?
A Grade D fire alarm is a mains-powered smoke or heat alarm with a built-in standby battery, so it keeps working during a power cut. The difference between the two sub-grades is the battery. A Grade D1 alarm has a sealed, tamper-proof battery. A Grade D2 alarm has a battery the user can replace. Where several alarms are fitted, they are normally interlinked by cable or radio so that when one alarm activates, they all sound.
Fire alarm categories: LD1, LD2 and LD3
The category describes where detectors are installed. "LD" categories are for the protection of life:
- LD1 (highest protection): detection throughout the dwelling, with detectors in all circulation areas that form part of the escape route and in all rooms where a fire might start (bathrooms, shower rooms and toilets are normally excluded).
- LD2 (medium protection): detectors in all circulation spaces that form part of the escape route, plus specified rooms or areas that present a high fire risk to occupants, including any kitchen and the principal habitable room (usually the main living room).
- LD3 (minimum protection): detectors only in the circulation spaces that form part of the escape route, such as hallways and landings.
BS 5839-6 also defines "PD" categories (PD1 and PD2) for the protection of property rather than life. They are used less often in homes.
Smoke or heat detection?
Smoke alarms suit hallways, landings and living rooms. In a kitchen, cooking fumes would cause false alarms, so BS 5839-6 recommends a heat alarm in every kitchen. You can compare optical smoke alarms, heat alarms and multi-sensor models in our smoke and heat alarms range.
Which grade and category do I need?
BS 5839-6 includes a table of minimum recommendations based on the type of premises, whether it is a new build or an existing home, and who lives there. Some examples from BS 5839-6:2019+A1:2020, as summarised in manufacturer guidance:
| Type of premises | Minimum grade | Minimum category |
|---|---|---|
| Rented homes (new build or existing) | D1 | LD2 |
| Existing HMOs of one or two storeys | D1 | LD2 |
| Owner-occupied new build houses of two or three storeys | D2 | LD2 |
| Self-catering or short-term holiday lets | D1 | LD1 |
| Sheltered housing, individual dwellings (new or materially altered) | D2 | LD1 |
Category LD3 is only the minimum for some existing owner-occupied homes, such as a bungalow, flat or two-storey house. Larger or higher-risk premises need more. These are minimums, and the right answer for a particular property depends on its layout, its occupants and the fire risk assessment. Legal requirements for rented homes also apply. Always check the full standard and current regulations, or ask a competent designer.
Carbon monoxide alarms and BS 5839-6
Carbon monoxide (CO) detection is a separate subject from fire detection. Domestic CO alarms are made to BS EN 50291. Under BS 5839-6, mains-powered CO alarms to BS EN 50291 may be interlinked with the fire detection system where the manufacturer of all the components recommends it. Some manufacturers, Aico among them, offer CO alarms that interlink with their own fire alarms, so check compatibility within one alarm family. See our carbon monoxide detectors for the range.
Testing and maintaining a domestic fire alarm
BS 5839-6 recommends that all systems other than Grade A are tested at least once a month, usually by pressing the test button on each alarm (see how to test smoke detectors). Follow the manufacturer's instructions for cleaning and replacing alarms at the end of their service life. Grade A systems follow a servicing regime closer to commercial systems. Their fire alarm panels and detectors should be maintained by a competent person.
Buying alarms for a BS 5839-6 system
- Choose the grade first: mains-powered with a sealed battery (D1) or with a replaceable battery (D2), or battery-only (F1/F2) where the standard allows it.
- Choose the category: plan smoke alarms for escape routes and add heat or smoke alarms to the rooms that LD2 or LD1 requires.
- Keep one alarm family across the property so that interlinking and bases are compatible.
- Add CO alarms where there are fuel-burning appliances, following the manufacturer's siting guidance.
JEM Systems UK supplies genuine, brand-new, factory-sealed alarms from leading brands, with fast, tracked UK delivery. Browse smoke and heat alarms, Aico, FireAngel and CO detectors. For HMOs and common areas, see our emergency lighting range.
Frequently asked questions
What is a Grade D1 fire alarm?
A Grade D1 alarm is mains powered and has a tamper-proof standby battery. It keeps working during a power cut, and the occupier cannot remove its battery.
What is the difference between LD1, LD2 and LD3?
LD3 covers the escape route only (hallways and landings). LD2 adds the kitchen, the principal habitable room and other high-risk rooms. LD1 covers the escape route and all rooms where a fire might start.
Is BS 5839-6 a legal requirement?
BS 5839-6 is a code of practice, not a law. However, regulations, building control bodies and housing enforcement officers often refer to it when they judge whether fire detection in a dwelling is adequate. Legislation such as smoke and CO alarm rules for rented homes may also apply.
What is the difference between BS 5839-1 and BS 5839-6?
BS 5839-1 covers fire detection and alarm systems in non-domestic premises. BS 5839-6 covers domestic premises, including houses, flats, HMOs and sheltered housing.
How often should domestic smoke alarms be tested?
BS 5839-6 recommends testing systems other than Grade A at least once a month, normally with the test button on each alarm.
This guide is general information; follow your fire risk assessment and a competent person's advice.