Everyone knows how important it is to have a smoke alarm in the home. If a fire breaks out while you’re asleep, the smoke it emits will set off the alarm, hopefully giving you time to get out before being asphyxiated by the fire’s deadly concoction of chemical gases.
But there’s another gas – carbon monoxide – that is possibly even more deadly because you can’t see it, smell it or taste it. Carbon monoxide (CO) is produced during incomplete combustion of fuels, usually because of a faulty appliance like a gas boiler, gas-powered fireplace, gas cooker, wood burner or blocked coal fire flue. Sadly, this writer has been on the receiving end of this silent killer – I lost a sister-in-law and her three dogs – so I’m doubly mindful of just how horrendously dangerous it can be. Like an invisible ghost in a horror movie, it enters a room, slowly sapping the life out of its occupants without anyone realising.
Thankfully, there is an early-warning solution in the form of a carbon monoxide alarm that costs only a few pounds more than a smoke alarm. Be aware, though, that not all CO detectors are sensitive enough and some no-name brands are downright useless – and therefore dangerous. Ensure you opt for a reputable brand like FireAngel, First Alert, Kidde, Nest or Lifesaver.
We’ve called in a quintet of CO alarms from top-name brands and put them to the test using the simple but effective ‘incense in a plastic bag’ method. We’ve also scoured the web for both professional and user reviews to back up our results. Read on for the lowdown and stay safe, people, stay safe.
How to select the best carbon monoxide alarm for you
What is carbon monoxide poisoning?
Carbon Monoxide is known as the silent killer because you can’t smell it, taste it or see it. Once it enters your bloodstream, it invades the red blood cells (haemoglobin), preventing them from carrying oxygen around the body. Symptoms of carbon monoxide poisoning include a flu-like headache, dizziness and nausea followed by tiredness, confusion, breathlessness, weakness, loss of muscular co-ordination and – dare I mention it – death. CO is so odourless that even dogs can’t detect it.
How do CO alarms work?
The health effects of CO depend on the concentration and length of exposure (carbon monoxide concentration is measured in parts per million). According to respected CO alarm manufacturer Kidde, ‘a carbon monoxide detector is a time-weighted alarm that measures the buildup of carbon monoxide in a house. For a person to begin feeling the effects of carbon monoxide poisoning, they would need to be exposed to a carbon monoxide level of 50 parts per million (PPM) for eight hours. An alarm’s response time will vary depending on the level of carbon monoxide in the air. For example, an alarm will sound after three and a half hours of continuous exposure at a level of 50 PPM, yet will sound after eight minutes of continuous exposure at a level of 400 PPM’.
Carbon monoxide alarms have a finite lifespan of between five and ten years. Even if the manufacturer states a seven-year lifespan, you should ideally change your CO monitor every six years just to be on the safe side. US tests have been carried out using some detectors over ten years old and some of them failed to detect even a whopping 1,000 PPM.
What levels of CO are considered dangerous?
Most people will not experience any symptoms from prolonged exposure to CO levels of under, say, 40 PPM. It depends on the length of exposure, but the real danger level starts at around 400 PPM (two to three hours of exposure at this level can be life-threatening). To give you some idea of how dangerous higher levels of concentration can be, 1,500 PPM could result in death within an hour and 6,000 PPM within 15 minutes.
All of these concentrations are bad enough when you’re awake and realise that something isn’t quite right – especially if others are feeling a similar effect – but if you’re asleep, you may wake up with a severe headache and nausea and be incapable of even crawling for fresh air. Worse, you might not even wake up at all.
Why should I be concerned?
According to the NHS, 25 people die every year in the UK from accidental CO poisoning. For extra peace of mind, you’re therefore advised to have your boiler, gas fire or wood/coal fire’s flue checked at regular intervals. And never ever use a gas-powered lamp or cooker inside a tent.
Where should I install my CO alarm?
Most manufacturers suggest locating your alarm next to or near to the gas appliance, 1.5 metres from the ground and at least 30cm away from ceilings. The Nest Protect notwithstanding, all of the models reviewed here can be placed on a worktop, shelf or table, and they can all be mounted to a wall. CO alarms aren’t just for brick and mortar homes either; they’re absolutely essential for caravans, motor homes and mobile homes.
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The best carbon monoxide alarms
Nest Protect: The best high-tech CO detector
Price:£99 | Buy now from Amazon
If you have a smartphone and can afford it, the Nest Protect is our top choice of carbon monoxide alarms, not least because it also detects smoke and works with an Android or iOS app. The Nest Protect is far and away the most aesthetically pleasing alarm and the most polite when it comes to false alarms. It also comes with way more tech than most, including a three-level LED lamp that lights the way in an emergency or when you get up in the middle of the night.
The Nest Protect is very easy to set up: simply remove the battery tab, launch the app, log in to your Wi-Fi, give it a name (kitchen, lounge etc) and mount it in a suitably elevated place on a wall.
Unlike other CO detectors, the Nest notifies you (and anyone else who has registered) with a notification on your mobile device, even if you’re in another country. It also does the same for smoke. The main unit also speaks a warning in a calm English female voice when it detects smoke or CO in a room. If the CO levels are slowly increasing, the voice will warn you before setting off the alarm. But if CO levels become dangerously high, the centre lamp glows red and a very loud, high-pitched beep is emitted along with a spoken warning letting you know which room is affected. You can temporarily cancel any alarms by holding the ‘stop’ button on the app or by pressing the unit’s big centre button.
The Nest Protect passed our sealed incense test with flying colours: the smoke alarm went off first followed by the CO alarm five minutes later; according to the app, the CO level was 414 PPM and increasing. Right now we can’t think of a better CO alarm on the market, particularly as it also detects smoke.
Key specs – Lifespan: 10 years; Battery type: 6 x AA; Display: none (uses smartphone app)
First Alert CO-FA-9B: The best budget carbon monoxide alarm
Price:£13 |Buy now from B&Q
Granted, this small 11cm x 7cm box is no pin-up, but it has one of the loudest-sounding alarms on test – excellent if it’s located well away from the bedroom. The First Alert is a doddle to set up – simply open the rear door, remove the pin between the battery connectors and place the unit on a shelf or mount it on a wall near your gas appliance.
At 50 PPM, this monitor has the most sensitive sensor in this roundup and that makes it an ideal choice for caravans and mobile homes. In our incense test, the First Alert sounded its extremely loud 85dB alarm after just three minutes of heavy CO exposure (about 400 PPM). If you’re looking for a cheap but very effective and – we hope – reliable travel-sized carbon monoxide alarm, then they don’t come much better than this.
Key specs – Lifespan: 7 years; Battery type: 2 x AA; Display: none
FireAngel CO-9D: A super-sensitive carbon monoxide alarm
Price:£18 | Buy now from Amazon
This excellent model from FireAngel comes with a 4.5cm LCD screen that displays both the temperature in the room and any concentrations of carbon monoxide, even if it’s just 1 PPM. After the Nest Protect, it’s the second best looker in the roundup.
This is a sealed unit with a seven-year lifespan/warranty and non-replaceable batteries. We would suggest replacing the whole unit a bit earlier, just to be on the safe side; you might want to set a calendar reminder in advance.
The FireAngel performed exceedingly well in our test, sounding the alarm when CO levels reached 357 PPM. However, its alarm beep wasn’t quite as loud as some others on this page and that could be an issue for anyone with hearing difficulties.
Key specs – Lifespan: 7 years; Battery type: Sealed; Display: 4.5cm LCD
Kidde 7DCO: The best CO detector for camping and travel
Price:£17 | Buy now from Amazon
Kidde produces a wide range of carbon monoxide detectors but we like this one because, while slightly ugly, it has a small LCD screen that displays CO readings from 10 PPM upwards. The Kidde’s sensor takes CO readings every 15 seconds and is a very sensitive thing indeed: it’s set to sound its 85dB alarm when carbon monoxide levels remain at 41 PPM for 60 minutes.
The 7DCO comes with a ten-year lifespan (longer than most) and is BS EN 50291-2 certified for camping, caravanning and travel. As with all CO detectors, the Kidde provides end-of-life and battery warnings (you need to replace the batteries every two years) and the obligatory test/reset button for peace of mind. We had no issues whatsoever during tests.
Key specs – Lifespan: 10 years; Battery type: 3 x AA; Display: LCD
Lifesaver 5CO
Price:£13 | Buy now from Argos
This cheap, award-winning model has a seven-year lifespan and runs on three replaceable AA batteries that last up to three years (it emits a reminder beep when they need to be replaced). Its sensor is set to sound the alarm after 60-90 minutes of exposure at 50 PPM. During our incense test, it sounded its raucous alarm after four minutes of exposure to 400 PPM of carbon monoxide.
The Lifesaver is actually manufactured by Kidde; the company keeps two brands going in order to gain maximum market share. Consequently, it doesn’t really matter which brand you choose as they both theoretically come from the same factory.
Key specs – Lifespan: 7 years; Battery type: 3 x AA; Display: None