CO Alarms for UK Log Burners — Legal Requirement Guide (2026)
CO alarms are legally required in any room with a fixed solid fuel appliance under UK Building Regulations Part J. BS EN 50291 certified, correctly positioned, £25–£40 buys a fully compliant 10-year sealed-battery alarm.
Legally required, not optional
Approved Document J §3.41 requires:
- A CO alarm complying with BS EN 50291 installed in any room containing a fixed solid fuel appliance
- Installation at the same timeas the stove (a HETAS-registered installer won't certify the installation without one)
- Positioned to detect CO before it reaches dangerous concentrations
For rented properties, the Smoke and Carbon Monoxide Alarm Regulations 2022 add additional landlord obligations including annual testing.
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
Bedrooms above the stove room should also have a CO alarm — CO is slightly lighter than air and 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 |
All four picks are BS EN 50291-1:2018 certified — the version required for UK Approved Document J compliance from 2018 onwards. Differences between them are marginal; buy whichever has the longest remaining warranty at point of purchase.
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 HETAS-registered installer or chimney sweep has inspected the flue and stove
- Report the incident to your local council's environmental health team
Frequently asked questions
Is a CO alarm legally required for a UK log burner?
Yes. Approved Document J requires a CO alarm in any room containing a fixed solid fuel appliance. The alarm must comply with BS EN 50291 and be installed at the time the stove is fitted. A HETAS-registered installer won't certify an install without one.
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?
For a log burner room, a 10-year sealed lithium battery alarm (£25–£40) is the standard UK choice — fully compliant with BS EN 50291 and Approved Document J, no wiring required, no annual battery changes. Mains-powered alarms are an unnecessary install complication for solid fuel.
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.