CO Alarms for UK Log Burners — Legal Requirement Guide (2026)
Every UK nation requires carbon monoxide warning provision when a new or replacement log burner is installed, but there is no single “UK Part J”. England and Wales publish separate Approved Documents J, Scotland uses its Building Standards Technical Handbook, and Northern Ireland uses Technical Booklet L.
Required across the UK under different rules
The four national guidance documents all require a suitable CO alarm when a new or replacement fixed combustion appliance is installed in a dwelling. For a log burner, that means:
- A CO alarm complying with BS EN 50291 provided in the room or space containing the appliance
- The alarm installed as part of the stove work, not treated as an optional accessory
- Positioned to detect CO before it reaches dangerous concentrations
Rental rules are also devolved. In England, the 2022 alarm regulations require relevant landlords to ensure an alarm is present, check it on the first day of a new tenancy, and repair or replace a reported faulty alarm as soon as reasonably practicable; they do not impose an annual CO-alarm test. Wales, Scotland and Northern Ireland have their own housing requirements.
Official rules by nation
- England: Approved Document J applies to building work in England.
- Wales: the Welsh Approved Document J has applied in its current form since 6 January 2025.
- Scotland: clause 3.20.20 of the Domestic Technical Handbook covers CO detection.
- Northern Ireland: regulation 72 and paragraphs 2.51–2.53 of Technical Booklet L cover CO warning and alarm placement.
Where to position the CO alarm
- Horizontal distance: between 1m and 3m from the stove
- Wall clearance: at least 300mm from any wall, if ceiling-mounted
- Height: ceiling-mounted, or wall-mounted at least 150mm below the ceiling
- Avoid: directly above the stove; corners and dead-air pockets; near windows, doors, or extractor fans; direct sunlight
Follow the alarm manufacturer’s instructions where they differ. Scottish and Welsh guidance also calls for early warning in a bedroom or principal habitable room through which a flue passes. Carbon monoxide mixes with room air, so do not position an alarm on the assumption that it simply rises.
UK 2026 picks
| Pick | Cert | Lifespan | Price |
|---|---|---|---|
Kidde 10LLDCO Best UK budget pick. Industry-standard reliability. | BS EN 50291-1:2018 | 10 years sealed | £25–£35 |
FireAngel CO-9X-10 Best for renters — visible end-of-life indicator. | BS EN 50291-1:2018 | 10 years sealed | £28–£40 |
Honeywell XC100D Best display — shows actual CO concentration. | BS EN 50291-1:2018 | 10 years sealed | £30–£42 |
Aico Ei208 Best for landlords — RadioLINK interconnection option. | BS EN 50291-1:2018 | 10 years sealed | £32–£45 |
These picks are sold as BS EN 50291-1:2018 certified. Check the marking on the exact unit, its replacement date and the current guidance for your nation before purchase; “UK Approved Document J compliance” is not a single nationwide designation.
10-year sealed vs replaceable battery
- 10-year sealed lithium (recommended): no battery changes for the lifetime of the unit. End-of-life chirp tells you to replace the whole alarm. The standard UK choice for solid fuel rooms.
- Replaceable battery: cheaper upfront (£15–£25) but requires annual battery checks. More prone to failure if owners forget to swap batteries.
- Mains-powered (with battery backup): typically used in newer-build homes where wiring was installed during construction. Overkill for retrofit log burner installs.
What a CO alarm actually detects
CO is a colourless, odourless gas produced by incomplete combustion of any carbon-based fuel. From a log burner, CO can accumulate in the room if:
- The flue is partially blocked (bird’s nest, soot buildup, debris)
- The chimney has structural cracks allowing flue gases to leak
- The stove door is open during low-temperature combustion
- Negative room pressure from extractor fans pulls combustion gases back into the room
- The stove is over-fired and quickly oxygen-starved
Symptoms of CO poisoning: headache, dizziness, nausea, confusion, then loss of consciousness. Above 800 ppm: death within hours. Above 12,000 ppm: death within minutes. A working CO alarm triggers at the long-exposure low concentrations (50 ppm) that cause chronic harm and short-exposure higher concentrations (300+ ppm) that cause acute harm.
If your CO alarm goes off
- Get everyone out of the property immediately
- Call 999 if anyone has symptoms
- Don’t go back in until the building is fully ventilated
- Don’t use the stove again until a suitably qualified solid-fuel installer or chimney professional has inspected the flue and stove
- Report the incident to your local council’s environmental health team
Frequently asked questions
Is a CO alarm required for a UK log burner?
For a new or replacement log burner, yes. England and Wales set the requirement in their separate Approved Documents J, Scotland in Technical Handbook clause 3.20.20, and Northern Ireland in Part L regulation 72 and Technical Booklet L. The alarm should comply with BS EN 50291 and be provided as part of the installation.
Where should the CO alarm be placed?
Between 1m and 3m horizontal distance from the stove, at least 300mm from any wall, mounted on the ceiling or high on the wall. Avoid corners and direct sunlight. Not directly above the stove.
How often should I replace the CO alarm?
Most CO alarms have a 5–10 year sensor lifespan stamped on the casing. After that the sensor degrades and may not trigger on real CO presence. Replace the whole unit, not just the battery. Sealed-battery models last 10 years; replaceable-battery models last 5–7 years.
Battery, mains, or hardwired CO alarm — which?
A sealed-life battery alarm is a common retrofit choice, while qualifying fixed mains-powered alarms are also allowed by national guidance. Check that the exact model meets BS EN 50291, follow its siting instructions and confirm the current requirements for the UK nation where it will be installed.
What’s the best CO alarm for UK log burners?
Kidde 10LLDCO, FireAngel CO-9X-10, and Honeywell XC100D are the most-installed UK 10-year sealed-battery picks. All BS EN 50291 certified, all £25–£40. Differences are marginal — buy whichever has the longest remaining warranty at point of purchase.