Best Carbon Monoxide Detector 2026: 10 CO and Smoke Alarms Ranked

This is both the most-reviewed and the best-scoring product on the page, and it is CO-only by design. An electrochemical sensor rated for 10 years does the detecting, two replaceable AA batteries do the powering, and the body works free-standing or on the included mounting bracket, so it can sit on a shelf beside a boiler rather than being fixed to a ceiling in the wrong room. That portability also makes it the one to throw in a bag for a caravan, boat or holiday cottage, which is exactly where unfamiliar appliances create risk.

A large test button checks it is working and doubles as a silencer for the low-battery chirp, and an amber flash warns when the cells need changing. At GBP 14.39 it is the cheapest way here to cover carbon monoxide properly.

It does not detect smoke, so it is not a substitute for a smoke alarm — pair it with one, or with the FireAngel set further down this page.

If you want one device covering both hazards, this is the best-evidenced choice on the page with 5,187 ratings at 4.5 stars. Its most useful feature is the voice notification: instead of leaving you to work out from a beep pattern whether you are dealing with smoke or carbon monoxide, it tells you, which is worth a great deal at three in the morning when nobody is thinking clearly.

A hush button silences a cooking-related false alarm without disabling the unit, there is a test and reset button, and a peak level memory records the highest CO concentration detected, so you can see whether something happened while you were out.

Being combined, it can only be in one place, which is the compromise described above. Kidde is one of the established names in this market, and at GBP 24.90 the two-in-one convenience is fairly priced.

The FA3820 is the fit-and-forget version of the top pick. Its 10-year battery is sealed inside and tamper-proof, so there is nothing to replace, nothing to run flat and nothing a child or a curious tenant can remove — you fit it and it works until the whole unit reaches end of life. That single difference is why many landlords and letting agents prefer sealed alarms.

It adds an enhanced sensing mode that activates if the alarm predicts CO levels are likely to rise, and an alarm memory that tells you a CO event happened while you were out — useful, because carbon monoxide can build and disperse without anyone noticing.

With 3,397 ratings at 4.6 stars it is well proven. At GBP 22.00 it costs more than the FA6813, and you cannot extend its life with new batteries, so you are paying up front for ten years of not thinking about it.

This is the sealed-battery combined alarm. It carries two distinct sensors — a photoelectric one for smoke and an electrochemical one for carbon monoxide — rather than trying to do both jobs with one element, and a built-in lithium battery powers it for ten years with nothing to change. A three-colour LED shows working status at a glance, which saves standing under it wondering whether the light means fine or faulty.

With 2,871 ratings at 4.6 stars it scores better than the Kidde, though on roughly half the sample.

Two notes. X-Sense states this model does not support interlinking, so it will not wire into a linked system where one alarm sounding triggers the others — worth checking against what your property needs. And as a combined unit it faces the same single-location compromise as the Kidde.

FireAngel's combined alarm covers both hazards with a 10-year battery and, usefully, gives smoke and carbon monoxide distinct alarm sounds along with clear visual indicators, so you can tell the two apart without a voice chip. Its optical sensing technology is designed to reduce nuisance alarms, which is the single most common reason people disable a smoke alarm and never re-enable it — the toast problem.

FireAngel lists it as suitable for a landing, hallway, bedroom, living room or dining room, and it has 1,359 ratings at 4.5 stars.

At GBP 29.97 it is the most expensive combined alarm here, and its review count is well under half the Kidde's. Choose it if reducing false alarms is your priority and you trust the FireAngel name; otherwise the Kidde and X-Sense give you more evidence for less money.

Most CO alarms tell you nothing until they scream. The FA3322 has a digital display showing the reading, plus temperature and humidity, so it doubles as a room monitor and, more importantly, gives you information rather than a binary. Its low-level warning is the real feature: when it detects low CO levels sustained over a period, it gives an early alert rather than waiting for a concentration high enough to trigger a full alarm — which is how a slowly failing appliance tends to show itself.

A 10-year battery is sealed within, and it has 686 ratings at 4.6 stars.

At GBP 39.99 it is the most expensive alarm on this page and detects CO only, so it needs a smoke alarm alongside. Buy it if you want visibility of what is happening rather than just an alarm, particularly if you have an older boiler or a solid fuel fire.

This unbranded listing undercuts every named combined alarm here at GBP 19.99 while offering a specification that reads well: independent photoelectric and electrochemical sensors rather than one shared element, a digital display giving a real-time CO readout, an 85dB sounder and standard replaceable batteries so it keeps going without buying a new unit every ten years. Mounting kits are included and it is pitched at homes, garages, offices and motorhomes.

It has 661 ratings at 4.5 stars, a reasonable sample for a listing of this kind.

The reservation is the same as with any unbranded safety product: there is no established company behind it, no service history, and no way to know the next batch is identical to the one these reviewers bought. For a device whose whole job is to work in an emergency years from now, that is worth weighing against the ten pounds you save over the Kidde.

The XP0A-SR pairs the feature that makes the Kidde good — an English voice alert naming the hazard rather than a beep code — with a body only 30mm thick, so it sits far less obtrusively on a ceiling than the usual bulky disc. It uses replaceable batteries rather than a sealed cell, which keeps the running cost down over a decade.

It has 345 ratings at 4.6 stars, the best score among the voice-equipped alarms here.

Two caveats. X-Sense states this model does not support interlinking, so it will not join a linked system. And 345 ratings is a small sample next to the thousands behind the Kidde, so the score is promising rather than settled. Buy it if you want voice alerts in a discreet unit and are comfortable with a newer listing.

This set is the practical answer to the problem described at the top of this page. Instead of one combined unit compromising on location, you get a dedicated SB1-R smoke alarm for the hallway or landing and the FA6813 CO detector — our top pick — to sit by the boiler or fire, for GBP 22.99, which is less than most single combined alarms here.

The smoke alarm uses a sensing chamber that sees smoke as it enters, and takes a one-year replaceable battery, while the CO alarm runs on its own replaceable cells with a 10-year sensor.

It sits at ninth only on evidence: 120 ratings is one of the smallest samples on the page, because it is a recent bundle rather than a new product — the FA6813 inside it has 8,477 ratings of its own. Note the smoke alarm's one-year battery needs annual attention, unlike the sealed ten-year units above.