Kidde 10SCO Combination Smoke & CO Alarm review
Test result

verdict: Outstanding
The Kidde 10SCO combination smoke and CO alarm is built to detect both smoke and carbon monoxide. This review covers how it fared in our tests when challenged to detect carbon monoxide back in 2018. It’s powered by a 9v battery and comes with a 10-year warranty and will sound to let you know when it’s reached the end of its working life. Read on for our full review to find out how this Kidde smoke and CO alarm fared in our detection tests.
- Outstanding at detecting all of the levels of CO we tested it with and continues to sound reliably even after being exposed to lots of CO. It also worked well after three months of usage.
- None that we found in our tests – this alarm sounded at the right time in every single one of our tests.
Unbranded Carbon Monoxide Alarm 1 review
Test result
verdict: Unresponsive to carbon monoxide – Don’t Buy
We have tested six alarms that look like the alarm pictured here between 2016 and 2018 and each has failed to detect the presence of carbon monoxide reliably in our tests. If the CO alarm in your home looks like the one shown, you will need to replace it because our tests prove that it’s likely to be unsafe. We’ve given alarms that look like this one our Don’t Buy warning, based on the six seemingly identical alarms that failed our CO tests.
- None – this is an unreliable carbon monoxide alarm that you shouldn’t buy.
- Everything we’ve seen in our testing shows that alarms that look like this can’t be relied upon to detect carbon monoxide (CO).
Each alarm we’ve tested has come with instructions which wrongly advise consumers to not install the alarm in the kitchen, where in many UK homes you’ll find a gas boiler, which could be a potential source of carbon monoxide (CO).
Unbranded Carbon monoxide alarm 2 review
Test result

verdict: Doesn’t detect CO every time – Don’t Buy
This carbon monoxide (CO) alarm is dangerous and failed to detect CO in two of our carbon monoxide detection tests. Following these gas detection failures, we’ve made it a Don’t Buy and our advice to you is to steer well clear of it. If you have one in your home, you should replace it with a well-known brand from a high street store or reputable online retailer.
- None – this is a dangerous alarm and should be avoided.
- Inability to detect carbon monoxide reliably
- Unhelpful and potentially dangerous instructions.
Unbranded Carbon monoxide alarm 3 review
Test result
verdict: Failed to detect carbon monoxide three times in our tests
This carbon monoxide (CO) alarm failed to sound in one of our initial carbon monoxide detection tests and also failed to respond and sound the alarm in two later gas tests. Because of this, we’ve made it a Don’t Buy. It’s sometimes known as the JKD-512COM, and in other listings it’s unbranded. Our tests show that you can’t rely on it to detect carbon monoxide every time, so our advice is to give it a very wide berth. If you have one in your home, replace it as soon as possible with an alarm from a well-known brand, and buy from a high street store or reputable online retailer.
- None – this alarm can’t detect carbon monoxide reliably.
- Poor at detecting carbon monoxide in our tests
- Too quiet
- Unhelpful and potentially dangerous instructions.
Unbranded Carbon monoxide alarm 4 review
Test result

verdict: Avoid this alarm – Don’t Buy.
This dangerous carbon monoxide (CO) alarm cannot be relied upon to detect CO and then sound the alarm when you need it to. That’s why we’re making it a Don’t Buy. It failed to detect CO in 17 of our detection tests and can’t be trusted to alert you if there’s a build-up of the deadly gas in your home. If you have this alarm, you should replace it as soon as possible with a model from a well-known brand.
- None – this alarm poses a danger to the lives of anyone who has one in their home.
- Inability to detect carbon monoxide reliably
- Too quiet
- Potentially unsafe instructions.
Unbranded Carbon monoxide alarm 5 review
Test result
verdict: Unreliable at detecting carbon monoxide – Don’t Buy
Bought from an online marketplace, this is yet another cheap and unbranded carbon monoxide (CO) alarm that you simply can’t rely on to detect CO. We’ve made it a Don’t Buy, as our test results show that after failing to detect CO three times, it’s more likely to endanger lives than to save them. If you have one in your home, replace it with an alarm from a well-known brand that’s available on the high street or from reputable online retailer.
- None – this dangerous alarm isn’t sensitive enough to detect CO reliably.
- Very poor CO detection in our tests.
Lifesaver Carbon Monoxide Alarm 5CO review
Test result

verdict: Excellent
The Lifesaver Carbon Monoxide Alarm 5CO comes with replaceable batteries that you’ll need to change every two to three years during its seven-year lifetime. In return for this upkeep, you’d expect to be able to rely on the Lifesaver Carbon Monoxide Alarm to live up to its reassuring name. To find out if this trust is justified, we tested it back in 2016 against four different levels of the poisonous gas in our test lab. Read on for the results of our test of this Lifesaver carbon monoxide alarm.
- Excellent at detecting all levels of carbon monoxide
- Loud enough for all to hear and robust enough to recover from a catastrophic gas incident to keep on working reliably.
- None. During three months of testing
- This alarm didn’t reveal any weaknesses.
Unbranded Carbon monoxide alarm 6 review
Product alert
Don’t Buy this carbon monoxide (CO) alarm – it failed to sound in all 38 of our carbon monoxide detection tests
This alarm simply can’t detect carbon monoxide (CO) and should be avoided. In our tests it failed to detect the gas every single time and that’s why we have made it a Don’t Buy.
Test result
verdict: Dangerously unreliable – Don’t Buy
This unbelievably dangerous carbon monoxide (CO) alarm failed to detect the deadly gas in every single one of our 38 tests. That’s why we’re making it a Don’t Buy. We bought it from eBay, but it’s also available from other online marketplaces. If you have an alarm that looks like this in your home, your best course of action is to replace it with an alarm from a well-known brand that you buy from a high street shop or reputable online retailer.
- None – this is a dangerous carbon monoxide alarm that you should avoid.
- Inability to detect carbon monoxide reliably.
Unbranded Carbon monoxide alarm 7 review
Test result
verdict: Dangerously unresponsive – Don’t Buy
This unsafe carbon monoxide (CO) alarm failed to detect the deadly gas in all but one of our tests – registering 37 failures to detect CO and sound the alarm – so we’re making it a Don’t Buy. We bought it from eBay, but it’s available from other online marketplaces too. In common with a collection of other cheap and unbranded alarms that we have bought and tested through this kind of site, you simply can’t rely on it to detect carbon monoxide when you need it to. If you have an alarm that looks like this in your home, replace it with a well-known brand from a high street store or reputable online retailer.
- None – this is a dangerously unreliable smoke alarm.
- Unable to successfully and reliably detect carbon monoxide
- Too quiet
- Misleading and potentially dangerous instructions.
Kidde Carbon Monoxide Alarm 7CO review
Test result

verdict: Very good indeed
You’ll need to replace the batteries in the Kidde Carbon Monoxide Alarm 7CO every two to three years, but in return it promises a decade of faithful service. So, is this 2016 carbon monoxide detector a worthwhile investment? We tested its ability to alert you to the presence of carbon monoxide in a series of exacting tests, and assessed the clarity of its alarm and installation instructions. Check our results to discover if this carbon monoxide detector has what it takes to be a Best Buy alarm.
- Excellent at detecting carbon monoxide
- Durable
- Resilient and loud enough for everyone to hear when the alarm sounds.
- None. During our extensive lab tests
- We found no drawbacks to this model.
Unbranded Carbon monoxide alarm 8 review
Test result
verdict: Dangerously unresponsive – Don’t Buy
This a Don’t Buy carbon monoxide alarm and it should be avoided. In our tests it failed to detect the deadly gas a worrying 27 times. It doubles as a <a href=”https://www.which.co.uk/reviews/smoke-alarms/unbranded-smoke-alarm-in-blue-box”>smoke alarm</a> and it was just as bad when we tested its smoke detection abilities. We bought it from a seller on eBay, but you’ll also find it listed on other similar online marketplaces. If you have one in your home, replace it with a well-known brand from the high street or a reputable online site.
- None – this is a dangerous alarm and one to avoid.
- Not sensitive enough to detect carbon monoxide reliably.
X-Sense CO03D review
Test result
verdict: Failed to detect CO every time – Don’t Buy
The X-Sense CO03D carbon monoxide alarm failed to sound in one of our carbon monoxide tests when we tested it in 2018. Because of the safety concerns we have based on the gas detection failure in our tests, we’ve made this X-Sense alarm a Don’t Buy. This product failed to sound when in the presence of a catastrophic concentration of carbon monoxide and all three of the samples of alarm we tested failed in the same way.
- It failed one of our carbon monoxide tests and passed all of the rest of them. But one failure is enough for us to slap a Don’t Buy warning on it.
- Three samples didn’t detect a huge concentration of carbon monoxide and that’s why we have made this alarm a Don’t Buy.
FireAngel CO-9B review
Test result

verdict: An excellent alarm
The FireAngel CO-9B Carbon Monoxide Alarm will last for seven years before you need to replace it, although you’ll need to change the batteries once or twice during its lifetime. It may need a touch more maintenance than some other carbon monoxide detectors, but does it reward your efforts with effective carbon monoxide detection? We tested it back in 2016, so read on for our test results.
- Outstanding at detecting low and high levels of carbon monoxide
- Reassuringly loud
- Just as good at detecting the gas on day 90 as it was on day one.
- Our three-month-long tests uncovered no weaknesses with this detector
FireAngel CO-9D review
Test result

verdict: Recommended
The FireAngel CO-9D Carbon Monoxide Alarm has a sealed battery, which means you’ll never have to buy replacements during its seven-year lifetime. It sounds like a convenient buy, but does it deliver where it really matters? To find out if you can trust this 2016 carbon monoxide detector when you need it most , we tested its reactions to different levels of carbon monoxide in a series of stringent safety tests.
- Detects carbon monoxide regardless of the amount in the room
- Very loud
- Reliable and resilient enough to recover from a catastrophic amount of carbon monoxide.
- Our three month-long tests uncovered no weaknesses with this alarm.
FireAngel CO-9X-10T-FF review
Test result

verdict: A very good alarm
If you buy the FireAngel CO-9X-10T-FF Carbon Monoxide Alarm you won’t need to replace it for a whole decade, which is about the top end of any carbon monoxide detector we’ve seen. It’s certainly long-lasting, but is it actually any good at sniffing out the deadly gas? We tested this FireAngel carbon monoxide detector back in 2016 to find out. Read on for the results of our carbon monoxide gas detection tests.
- Excellent at detecting carbon monoxide
- Loud enough to wake up the neighbours
- Reliable and robust enough to recover from a serious gas incident and continue to detect well.
- Our three-month-long tests didn’t uncover any weaknesses in this alarm’s performance.
FireAngel CO-9X review
Test result

verdict: Excellent in our tests
If you’re looking for a device that needs minimal maintenance, then the FireAngel CO-9X Carbon Monoxide Alarm may well catch your eye. It has a sealed battery, which means you won’t have to replace the batteries during its seven-year lifetime. We’ve tested its detection of killer carbon monoxide in a series of stringent lab tests back in 2016 to see if it pairs convenience with the quick reactions you need to keep you and your family safe in an emergency. Read on for the results of our tests.
- Brilliant at detecting different levels of carbon monoxide
- Reliable
- Loud enough for all to hear
- And robust enough to recover and continue to work following a serious carbon monoxide leak.
- None. Our three-month-long tests uncovered no weaknesses with this alarm.
Aico Ei208 review
Test result
verdict: Imperfect in our tests
The Aico Ei208 carbon monoxide alarm failed to sound in one of our 2018 carbon monoxide tests and that’s why we’ve made it a Don’t Buy. In one of our tests, we flooded three of the Aico alarms with a catastrophic level of carbon monoxide to which they responded correctly and sounded. But later, when we tested them with a lower but still dangerous level of the gas, none of the three alarms sounded. Aico told us that it’s concerned, that it takes all matters of alarm quality and reliability very seriously, that all of its alarms are independently tested, it hasn’t had a problem with these alarms since they were launched in 2010, and that it is confident its alarms meet the carbon monoxide alarms standard.
- This alarm passed all but one of our tests. But because of the gas detection failure we found in one of our tests
- We have made it a Don’t Buy.
- The alarm failed to recover and sound following being exposed to a very high level of CO.
Kidde Long Life Carbon Monoxide Alarm 10LLCO review
Test result

verdict: First-class
The clue is in the name of the Kidde Long Life Carbon Monoxide Alarm 10LLCO – it should last up to 10 years before you’ll need to replace it. Along the way you won’t even need to replace the batteries, which are safely sealed inside the unit. But does it pair this long life with the ability to detect even small concentrations of carbon monoxide in the air? We put the Kidde carbon monoxide detector through a series of gas detection tests back in 2016 to find out.
- Effectively detected carbon monoxide at four different strengths
- Loud
- Durable and resilient enough to recover from a carbon monoxide drenching to carry on working reliably.
- None. During three months of testing this alarm didn’t reveal any weaknesses.
Nest Protect Smoke + CO Alarm review
Test result

verdict: Truly outstanding
The Nest Protect Smoke + CO Alarm can send alerts about dangerous levels of carbon monoxide or smoke direct to your smartphone, which is a handy touch if you’re out of the house at the time. This more advanced two-in-one functionality, along with its 10-year lifespan, pushes the price up far above the price of a standard CO alarm. This review is of how well the Nest detects CO, but it’s also a smoke alarm and since testing it, the law on smoke alarms has changed in Scotland. This means that as the Nest doesn’t come with a heat detection function, it won’t be suitable for Scottish homes from 2022. We put the Nest Protect Smoke + CO Alarm through a series of stringent carbon monoxide safety detection tests to find out how well it detects the deadly gas. Read on for the results of our tests.
- The smartphone alerts work well
- It’s great at detecting various levels of carbon monoxide
- Survives extremely high levels of the gas and is loud enough for everyone to hear.
- Only the high price
- But it is two products in one and will last for 10 years.
FireAngel W2-CO-10XQ review
Test result

verdict: Responsive and impressive
Offering a market-leading 10-year lifetime, the FireAngel W2-CO-10XQ promises a full decade of service before you need to replace it. Does it pair this long life with a first-class ability to detect poisonous gas? To find out we put this carbon monoxide alarm through a full range of safety tests back in 2016, assessing everything from the clarity of its alarm sound to how sensitive it is to four different levels of carbon monoxide. Read on for our summary of how this FireAngel carbon monoxide alarm fared in our lab tests.
- Effective at detecting different concentrations of carbon monoxide
- Reliable enough to keep on working after being exposed to high concentrations of the gas and loud enough to wake you in an emergency.
- It costs around twice as much as other models with a similar lifetime guarantee.
Kidde 4MCO review
Test result
verdict: An excellent alarm
The Kidde 4MCO mains-powered carbon monoxide (CO) alarm is designed to last for seven years before it will need to be replaced. It comes with a rechargeable backup battery so that it will sound even during a power cut. A test button allows you to check it’s working and the alarm chirps to let you know when it reaches the end of its life. It can be connected to other Kidde alarms so that if one detects danger, they will all sound. We tested the Kidde 4MCO – the 4MDCO is identical other than it has a digital display. We tested the Kidde 4MCO back in 2019 to find out how well it detected a variety of concentrations of carbon monoxide. Read on for our verdict on this mains-powered carbon monoxide alarm and to find out whether this is the right alarm for you.
- Excellent at detecting both low and high levels of carbon monoxide
- Loud enough for all to hear.
- None in terms of how it performed
- Mains alarms are more pricey than battery-powered counterparts.
Ei Electronics Ei3018 review
Test result
verdict: Very impressive
The mains-powered Ei Electronics Ei3018 carbon monoxide alarm is built to detect CO for five years and has a warranty to cover this. There is a backup rechargeable battery, which kicks in if there’s a power cut. The alarm can be used in a network of other Aico/Ei alarms, so that if one detects danger, they all sound. You’ll need the Ei3000MRF interlink module (£48) to do this, which also sends data to your smartphone regarding when it detects CO. To find out how well this Ei Electronics mains-powered CO alarm detects the deadly gas, we tested it in 2019. Read on for our verdict on this alarm.
- Brilliant at detecting carbon monoxide regardless of the amount of the gas we tested it with
- Easily loud enough.
- None we found in our tests
- More expensive than a battery-powered CO alarm would be.
Honeywell XC100 review
Test result

verdict: A very good CO alarm
The Honeywell XC100 carbon monoxide alarm is built with longevity in mind. It comes with a sealed-in and tamper-proof 10-year battery, so you won’t need to worry about finding replacement batteries for it. It also comes with a backlit warning message in red, which shows through the case. When there’s CO in the air, the Honeywell not only sounds, but also displays the message ‘Alarm evacuate’. But how well does it detect carbon monoxide? To find out, we tested it back in 2018. Read on for the full results.
- Detects when carbon monoxide is at dangerous levels and sounded the alarm every time in our tests.
- None that surfaced in our tests.