CO2 poisoning can be not only harmful but deadly, so having a carbon monoxide alarm installed could potentially save your life in case of a CO leak. Carbon monoxide detectors work the same way as a smoke detector or a heat detector, in the sense that it sounds an alarm when it detects danger, only that it is designed to pick up the presence of carbon monoxide in the air. Below, you’ll find out why CO is dangerous, how a CO alarm works and what to do if it goes off. 

Why do I need a CO detector? 

Silent, invisible and odourless, carbon monoxide is a poisonous gas that is often referred to as the Silent Killer. Carbon monoxide poisoning can cause sudden illness and even death. In fact, the statistics show that in England and Wales, 60 people on average die from CO poisoning per year. 

If you use any sort of a fuel-burning appliance in your home, such as boiler, cookers, central heating, water heaters, you could be in danger of a CO leak. Running car engines, as well as gas fires and any other open fires, could also dangerously increase the carbon monoxide levels in your home.

Carbon monoxide is produced when fuels such as oil, gas and wood burn insufficiently. It enters your bloodstream when breathed in and it prevents your blood from carrying oxygen, causing the cells within your body to die. 

Some of the signs of carbon monoxide poisoning include dizziness, shortness of breath, confusion, stomach ache and feeling sick. The longer you are exposed to a CO2 leak, the more severe the effects become. The initial symptoms are flu-like but CO2 exposure can eventually lead to brain damage and death. 

Having a carbon monoxide detector installed means that you will be alerted to the danger that would otherwise be undetectable before it’s too late. 

When will my carbon monoxide detector sound the alarm?

Most people won’t feel sick or notice any symptoms of carbon monoxide poisoning at a concentration of less than 70 ppm. However, a carbon monoxide detector can go off at 50 ppm if this level concentration has been present for at least eight hours. If the CO levels are dangerously high, the alarm can be triggered within minutes. 

It is important to take action as soon as the CO alarm goes off because prolonged exposure to low levels of CO can be as dangerous as sudden exposure to extremely high levels (150ppm and above), due to the buildup in your bloodstream. 

What to do when the CO detector goes off

The first rule of dealing with any emergency situation, including a potential CO leak, is to stay calm. Then you should take the following steps:

  • Open as many doors and windows as possible to get fresh air in
  • Take everyone on the premises outside to avoid CO poisoning
  • Check everyone for CO poisoning symptoms. If you spot any, call 999.
  • Report the incident to the gas emergency authority on 0800 111 999 
  • Ensure all potentially dangerous appliances are properly and regularly maintained in the future.

How to choose the best carbon monoxide detector? 

As with most other products, CO detectors are not all equally reliable, so choosing the right one can make the difference between life and death. Below we’ll look at some of the factors to consider when buying a carbon monoxide detector.


The average price of a carbon monoxide detector is about £20, with premium models going over £25. You could get a cheaper deal around £17 but if the CO detector costs under £10, this should raise some red flags, as many detectors in that price range have been deemed unsafe during independent lab testing. 


For a carbon monoxide detector to be considered safe and effective, it must be compliant with the latest relevant industry standards. Before you buy a product, check whether it has been approved under the BSI Kitemark of the EN50291 European standard. 

Sealed vs replaceable battery vs mains powered

Most carbon monoxide detectors run on batteries. When the battery is close to running out, your detectors will begin chirping to notify you that it needs to be replaced. If you opt in for a replaceable battery CO detector, you will have to buy a new battery every two or three years. If you choose a sealed battery unit, you will have to replace the entire CO detectors once the chirping begins. However, you won’t have to worry about that for at least 10 years. If you don’t want to have to deal with replacing batteries at all, you should go for a mains powered CO alarm

Smart functionality 

If you are willing to invest in buying the best carbon monoxide detector out there, you might want to look into the smart detector options. Some modern units can be connected to your phone and set up to send you notifications if the CO levels in your home are too high, even when you are not there. Also, some CO alarms, such as the Fire Angel CO- 9B can indicate the danger level to give you a better understanding of the severity of the situation. 

Head over to our article on CO Detector issues if you want to learn more about some of the most prevalent issues surrounding them.


Are smoke detectors and carbon monoxide detectors the same thing?

No, they are not. Smoke detectors alert you to the presence of smoke on the premises while CO detectors check for dangerously high levels of carbon monoxide in the air. 

Is having a carbon monoxide detector a legal requirement in the UK?

Yes, according to the Smoke and Carbon Monoxide Alarm (England) Regulations 2015, landlords are required by law to install at least one carbon monoxide detector on every floor of a residential building or in every room where a solid fuel-burning appliance is present.

What does it mean if your carbon monoxide detector beeps?

If your carbon monoxide detector is beeping or chirping, it probably means that the battery is running low and needs to be replaced. 

Can opening a window stop carbon monoxide poisoning?

Opening a window can improve ventilation and slow down carbon monoxide poisoning. However, it is not going to eliminate the danger completely. You would have to find the source of the leak and address the issue to prevent further exposure. If you have symptoms of CO poisoning, contact the emergency services immediately. 

How to test if your carbon monoxide detector is working?

If the model of your unit allows for testing, it should have a “Test” button. Once you find it, press until you hear two beeps. Release the button and then repeat the procedure, this time until you hear four beeps. 

Are there any alternatives to a CO detector?

A cheaper way to detect carbon monoxide is CO patches. Those can be placed in any room and they will change colour if a carbon monoxide leak is detected. However, they will not sound an alarm and unless you are specifically checking them, you will not know that there is a danger of CO poisoning. This makes them a far less effective solution to the problem than a CO detector.