Carbon monoxide poisoning kills around 40 people in the UK every year and sends more than 4,000 to hospital, according to the NHS. The gas is invisible and odourless, so a detector is the only reliable way to know it is present. A smart carbon monoxide detector goes further — it sends push notifications to your phone the moment CO is detected, so you can act even if you are away from home or asleep with headphones in.
All CO alarms sold in the UK must comply with BS EN 50291, the European standard for electrochemical CO sensing. Building Regulations Approved Document J also requires a CO alarm wherever a new or replacement solid-fuel appliance (log burner, open fire, biomass boiler) is installed — and good practice extends that to any gas appliance including boilers, fires, and cookers.
What to Look for in a Smart CO Detector
BS EN 50291 certification. Every alarm on this list carries the standard. Do not buy any detector — smart or otherwise — that does not display this mark.
Electrochemical vs semiconductor sensing. Electrochemical cells are the gold standard for domestic CO detection: they are highly accurate, less prone to false alarms, and are required by BS EN 50291. Cheaper semiconductor sensors (found on some DIY IoT boards) are not compliant for mains-replacement use.
Wireless interlink. If one alarm triggers, all alarms in the home sound simultaneously. This is especially important in larger properties or where bedrooms are far from the boiler room. Look for either proprietary RF interlink (FireAngel, ei Electronics) or Wi-Fi/matter interlink (Nest Protect).
Placement. CO alarms should be fitted within 3 metres of every fuel-burning appliance and in every bedroom where occupants sleep with the door closed, at roughly head height (1–1.5 m above the floor). Never place a CO alarm directly above a gas hob — cooking fumes can temporarily spike CO readings.
For a broader look at home safety, our guide to the best home security systems UK covers integrated platforms that combine alarms, cameras, and sensors in one app.
The Best Smart CO Detectors in the UK
1. Google Nest Protect — Best Overall (£109.99)
Combined smoke and CO. The Nest Protect remains the benchmark smart alarm in the UK. It detects both carbon monoxide and smoke (split-spectrum for fast-flaming and slow-smouldering fires), speaks aloud to tell you which room the threat is in, and sends instant push notifications via the Google Home app. Alarms interlink over Wi-Fi and 802.15.4 (Nest Weave), so all units sound when any one is triggered.
The Nest Protect is available in wired (240 V AC) and battery versions. Battery life is quoted at around five years from a set of six AA cells. The built-in Pathlight feature also doubles as a subtle night-light when you walk past in the dark.
At £109.99 per unit it is the most expensive alarm here, but the combination of smoke and CO sensing, a polished app, and Google Home integration makes it excellent value if you are already in the Google ecosystem. It meets BS EN 50291 for CO detection and BS EN 14604 for smoke detection.
Check Nest Protect price on Amazon
2. FireAngel Pro Connected — Best Mid-Range (~£49.99)
Wi-Fi + wireless interlink. FireAngel is one of the UK's most trusted fire-safety brands, and the Pro Connected range brings app connectivity to their proven hardware. The CO alarm pairs to the FireAngel Connected app (iOS/Android) via a dedicated Wi-Fi gateway or built-in Wi-Fi depending on model, delivering remote alerts and alarm history.
The Pro Connected range supports FireAngel's W2-RF wireless interlink protocol, so you can mix and match CO and smoke alarms across an entire property and they will all sound together. This makes it ideal for larger UK homes where the boiler is in a separate utility room or basement. Sensors meet BS EN 50291.
Check FireAngel Pro Connected on Amazon
3. ei Electronics ei208W — Best for Wireless Interlink (~£44.99)
RadioLINK+ wireless mesh. ei Electronics (part of Aico) makes alarms specified by many UK social housing providers and local authorities. The ei208W is a mains-powered CO alarm with a wireless RadioLINK+ module built in. It interlinks with the full range of Aico alarms — smoke, heat, and CO — forming a whole-home safety mesh without the need to run extra cables.
The alarm does not have a consumer smartphone app in the traditional sense, but it can connect to the Aico HomeLINK gateway for remote monitoring, data logging, and landlord compliance dashboards. For homeowners who want a more professional-grade interlinked system — particularly where Building Regulations require multiple alarms — ei Electronics is the preferred choice among UK fire-safety engineers.
4. Kidde 10SCO — Best Budget Smart Option (~£29.99)
Combination alarm at an accessible price. The Kidde 10SCO is a combined smoke and CO alarm that connects to the Kidde app for remote alerts and self-test. It is battery-powered (10-year sealed battery), so there is no wiring required — suitable for renters or for rooms without a mains spur nearby.
The 10SCO lacks wireless interlink, which is its main limitation. It is best deployed as a standalone unit near a single appliance — for example, a gas boiler in a kitchen or utility room — rather than as the backbone of a whole-home system. Meets BS EN 50291.
UK Legal Requirements for CO Alarms
Since October 2022, amended Building Regulations (Approved Document J) require a CO alarm to be fitted in any room with a new or replacement fixed combustion appliance (boilers, gas fires, log burners) in all domestic premises in England. Scotland, Wales, and Northern Ireland have similar — and in some cases stricter — requirements under their own building regulations.
For rented properties in England, the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 require landlords to fit a CO alarm in every room with a gas, oil, or solid-fuel appliance. Failure to comply can result in a fine of up to £5,000.
Even where not legally mandated, the NHS and the Gas Safe Register recommend fitting a CO alarm near every fuel-burning appliance in the home.
Where to Place Your CO Alarm
Within 3 metres of every fuel-burning appliance — this includes gas boilers, gas fires, log burners, oil-fired boilers, and solid-fuel ranges. Place the alarm at approximately head height (1–1.5 m from the floor), or follow the manufacturer's instructions if they differ.
In every bedroom — CO can accumulate overnight without waking you. If you have a gas boiler on an external wall adjacent to a bedroom, fitting an alarm in that room provides an important additional layer of protection.
Not in the kitchen directly above a hob — normal cooking activity can produce brief CO spikes that may trigger nuisance alarms. Site the alarm on a nearby wall or adjacent room instead.
If you are also reviewing your wider home-safety setup, see our roundup of the best smart smoke detectors UK for alarms that cover fire detection in the same interlinked system.
CO Alarm Maintenance
BS EN 50291 defines a minimum sensor lifespan of five years for battery-powered alarms and seven years for mains-powered units, after which the entire unit should be replaced — not just the battery. Mark the installation date on the back of the alarm and set a calendar reminder. Most smart alarms will notify you via the app when the sensor is approaching end of life.
Test your alarm monthly using the test button. Never use naked flames to test a CO alarm — only purpose-made test gases (available from alarm suppliers) should be used if you need to verify sensor response beyond a functional test.
