Best carbon monoxide alarms for UK homes (2026)
A carbon monoxide alarm is one of the few bits of safety kit that genuinely saves lives for under £25 — CO is invisible, odourless, and produced by any fuel-burning appliance from a boiler to a camping stove used indoors. If your home has gas, oil, solid fuel or an open flame anywhere, you need one. Here's how to pick a good one and where to put it.
By Tom Rowland · Updated 18 July 2026 · 6 products, price-tracked
Before you buy
The one spec that matters is the standard: a CO alarm must be marked EN 50291 (the British/European standard) and ideally carry a Kitemark or equivalent. That's what tells you it's been independently tested to detect CO at the right levels and sound in time. A cheap unbadged detector is worse than useless because it breeds false confidence.
After that, it's about sensor life and power. CO sensors don't last forever — most alarms have a sealed 7-year or 10-year life and then must be replaced (the alarm bleeps at end of life). Sealed-battery models (FireAngel, Honeywell) need no battery changes for their whole life; replaceable-battery models are cheaper upfront. A digital display is a nice-to-have that shows CO levels and helps you spot a low-level chronic leak, not just an emergency.
Placement is part of buying: fit an alarm in every room with a fuel-burning appliance, roughly at head height and about 1–3 metres horizontally from the appliance — not right next to it, and not in a sealed cupboard. Test it monthly and note the replacement date. If it ever sounds, get everyone out into fresh air and call the gas emergency line (0800 111 999) or 999.
Top pick: Aico Ei208 Carbon Monoxide Alarm. A professional-grade CO alarm from a trusted UK manufacturer, with a sealed 10-year lithium battery so there are no cells to change and nothing to forget. It costs more than a supermarket alarm, but the electrochemical sensor and BS EN 50291 Kitemark make it a sensible long-term buy for any home that burns fuel.
| Alarm | Standard | Sensor life | Display | Power | Price | |
|---|---|---|---|---|---|---|
| Aico Ei208 Carbon Monoxide AlarmTOP PICK | BS EN 50291-1:2018 (Kitemarked) | 10 yr | None (LED status indicators) | Sealed 10-year lithium battery (non-replaceable) | £26.00at usual price | Check price → |
| Kidde 5CO Carbon Monoxide Alarm | BS EN 50291-1, Kitemarked | 10 yr | LED only (no digital readout) | 2 x AA (replaceable, supplied) | £15.00at usual price | Check price → |
| X-Sense CO03D Carbon Monoxide Detector | EN 50291 | 10 yr | LCD digital (real-time CO ppm, backlit) | 3 x AA replaceable batteries | £23.00at usual price | Check price → |
| Honeywell XC100 Carbon Monoxide Alarm | BS EN 50291-1:2010 (Kitemarked) | 10 yr | LED indicators only (no digital readout) | Sealed 10-year lithium battery (non-replaceable) | £33.00at usual price | Check price → |
| FireAngel CO-9X Carbon Monoxide Alarm | EN 50291-1:2010+A1:2012 | 7 yr | LED status lights (no digital readout) | Sealed 7-year lithium power pack (non-replaceable) | £22.00at usual price | Check price → |
| Google Nest Protect (Smoke + CO Alarm) | EN 14604 (smoke) + EN 50291-1 (CO) | 10 yr | Colour LED status ring + voice alerts (no numeric readout) | Battery (6x AA lithium) or mains-wired 230V with AA backup | £109.00at usual price | Check price → |
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Aico Ei208 Carbon Monoxide Alarm
Who it's for: Households with a gas boiler, hob, open fire or wood burner who want fit-and-forget protection.
A professional-grade CO alarm from a trusted UK manufacturer, with a sealed 10-year lithium battery so there are no cells to change and nothing to forget. It costs more than a supermarket alarm, but the electrochemical sensor and BS EN 50291 Kitemark make it a sensible long-term buy for any home that burns fuel.
- Sealed 10-year lithium battery means no battery changes and no low-battery beeps for a decade
- Proven electrochemical sensor, factory-calibrated to CO gas and meeting BS EN 50291-1:2018 with a Kitemark
- AudioLINK+ lets you pull an alarm-status report to your phone, useful for landlords and checking history
- No digital display, so you cannot see a live CO ppm reading at a glance
- Dearer than budget alarms, and the whole unit must be replaced at end of life rather than just the battery
Don't buy if You want a live digital ppm readout, or you need alarms that interlink across the house so one sounding triggers the rest, in which case choose a display model or the RadioLINK Ei208WRF instead.
Kidde 5CO Carbon Monoxide Alarm
Who it's for: An affordable, standards-approved CO alarm for a room with a gas boiler, fire or stove.
A dependable, no-frills carbon monoxide alarm from a well-known brand, Kitemarked to BS EN 50291 with a 10-year sensor. It does the essential job well, though there is no digital readout and you will need to keep the AA batteries fresh.
- Kitemarked to BS EN 50291-1 with a 10-year sensor life from a trusted brand
- Inexpensive and widely stocked at UK retailers
- Simple to fit, wall-mounted or freestanding, with batteries and fixings supplied
- LED indicators only, so you cannot read the actual CO ppm level
- Uses replaceable AA batteries rather than a sealed 10-year cell, so they must be kept charged
Don't buy if You want a digital display showing live CO levels or a fully sealed battery you never have to touch, in which case the digital 5DCO or a sealed-battery model suits better.
X-Sense CO03D Carbon Monoxide Detector
Who it's for: Households who want a clear digital CO readout without paying premium-brand money.
A dependable, EN 50291-compliant CO alarm that shows the actual CO level on its screen rather than just sounding off, at a genuinely low price. The 10-year sensor life and replaceable AA batteries make it easy to live with, though it works alone rather than linking to other alarms.
- Certified to EN 50291, the standard UK CO alarms should meet
- LCD shows real-time CO concentration in ppm, not just an alarm tone
- 10-year sensor lifespan and low price make it strong value
- Standalone only, it won't interconnect with alarms elsewhere in the house (the separate CO03D-W does)
- Uses replaceable AA batteries rather than a sealed 10-year cell, so you'll swap them periodically
Don't buy if You want a fully sealed, fit-and-forget 10-year unit with no battery changes, or a whole-home system where every alarm sounds together, in which case choose a sealed-battery or interconnected model instead.
Honeywell XC100 Carbon Monoxide Alarm
Who it's for: Fit-and-forget CO protection for a decade with no battery changes.
A well-certified, Kitemarked alarm from a trusted brand, with a sealed 10-year battery so there is nothing to replace until it retires. The plain XC100 gives an LED-and-sounder alert only, and it is now being phased out in favour of newer X-Series models, so check the warranty date on what you receive.
- Kitemarked and certified to BS EN 50291-1:2010, the UK domestic CO standard
- Sealed 10-year lithium battery means no annual battery fiddling
- Flexible mounting (wall, ceiling or free-standing) with a 90dB sounder plus LED alert
- LED indicators only, with no digital ppm readout (you need the XC100D for that)
- Now discontinued and being superseded, so remaining stock may already have some of its 10-year life used up
Don't buy if You want to see the actual carbon monoxide level in ppm, or you would rather buy a current model with a full, fresh 10-year warranty. In those cases look at the XC100D (digital display) or the newer X-Series alarms instead.
FireAngel CO-9X Carbon Monoxide Alarm
Who it's for: Basic, maintenance-free CO cover next to a boiler, gas hob or open fire.
A dependable, no-frills alarm that meets the EN 50291 standard and runs for seven years on a sealed battery, so there is nothing to maintain. It does the essential job well, but the LED-only design and shorter life have been overtaken by newer 10-year models.
- Sealed 7-year power pack means no battery changes and no low-battery chirps to chase
- Certified to EN 50291, the UK standard for domestic CO alarms
- Simple, low-cost way to protect a room with a gas or solid-fuel appliance
- LED status lights only, with no digital display of CO levels
- 7-year life is shorter than the 10-year alarms now standard, and the model is being phased out
Don't buy if You want a digital screen showing live CO readings, or the longest service life, in which case a current 10-year model such as the FireAngel CO-9X-10 or FA3820 is the better buy.
Google Nest Protect (Smoke + CO Alarm)
Who it's for: Households already in the Google/Nest ecosystem wanting one interconnected smoke-and-CO unit with phone alerts.
A genuinely capable combined smoke and CO alarm that self-tests its sensors, interconnects wirelessly and sends alerts to your phone. Bear in mind Google discontinued the line in 2025 with no directly-available UK replacement, which is worth weighing before committing to a device meant to last a decade.
- One unit covers both smoke and CO, meeting EN 14604 and EN 50291-1
- Automatically checks its sensors and battery, with app alerts and phone hush
- Wirelessly interconnects so every alarm in the home sounds together
- Split-spectrum sensor responds to both fast-flaming and slow smouldering fires
- Far dearer than a standard alarm (£100+ versus £15-40)
- Discontinued by Google in 2025, with no direct UK successor and smart features tied to Wi-Fi and the app
Don't buy if You simply need dependable, no-fuss protection: a standard sealed 10-year smoke or CO alarm at £15-40 does the core safety job just as well, and you may prefer a product line that is still supported.
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Common questions
Do I really need a carbon monoxide alarm?
Yes, if your home has any fuel-burning appliance — a gas or oil boiler, gas hob, open fire, wood burner or similar. CO is invisible and odourless, and an alarm is the only way to detect it. It's cheap, life-saving and, in many rented homes, a legal requirement.
What standard should a CO alarm meet?
Look for EN 50291 marked on the alarm, ideally with a Kitemark or equivalent third-party certification. That confirms it's been independently tested to detect carbon monoxide at the correct levels. Avoid any detector that doesn't clearly state the standard.
Is a carbon monoxide alarm the same as a smoke alarm?
No — they detect different things and you need both. A smoke alarm detects fire; a CO alarm detects carbon monoxide gas. Some combined units (like Nest Protect) do both, but a standard smoke alarm will not warn you about CO.
How long do CO alarms last?
The sensor has a limited life — typically a sealed 7 or 10 years — after which the alarm signals end of life and must be replaced. Sealed-battery models last their whole life with no battery changes; replaceable-battery ones are cheaper but need new batteries.
Where should I put a carbon monoxide alarm?
In each room with a fuel-burning appliance, at about head height and roughly 1–3 metres horizontally from the appliance — not directly above or beside it, and not shut in a cupboard. Test it monthly.
What do I do if my CO alarm goes off?
Get everyone out into fresh air immediately, don't stay to investigate, and call the free national gas emergency line on 0800 111 999 (or 999 if anyone is unwell). Only return when you're told it's safe.