Where to place a carbon monoxide detector, and how it works

19 January 2021 | Celia Topping

carbon monoxide detector poison guide

What is carbon monoxide, and how is it produced?

Carbon monoxide is a highly toxic gas. It’s produced by the incomplete burning of fuels such as gas, oil, wood and coal. Breathing it in, even for a short time, can cause serious organ damage, and even death. 

Incomplete burning of fuel can happen when appliances such as boilers, cookers and ovens are:

  • Incorrectly fitted
  • Not properly maintained
  • If their vents become blocked

It’s not just gas-burning products that pose a carbon monoxide risk. Any appliance that burns fuel can produce carbon monoxide. This includes heaters, oil-fired boilers, car engines, and fires.

This deadly gas is especially dangerous because it’s colourless, tasteless and odourless, making a leak very difficult to spot. For this reason, carbon monoxide is known as the “silent killer”. This is why it’s absolutely crucial that you have a working carbon monoxide detector in your home. 

To find out how to spot warning signs of a carbon monoxide leak, read our comprehensive guide. 

Where to place a carbon monoxide detector

Carbon monoxide detectors save lives. Knowing where to install these detectors is vital to protect you and your family against this poisonous gas. 

  • Put a detector in every room that contains a fuel-burning appliance, or in a central location, such as a hallway or a landing. 
  • If you’re only installing one detector, put it near your bedroom so you’ll definitely hear it if you’re asleep.
  • Do not place the detector near a fireplace, or flame-producing appliance.
  • Make sure the alarm is at least one metre away from fuel-burning appliances, such as boilers and ovens.
  • The alarm should be placed at head height (breathing level). It doesn’t have to be fixed on a wall – you could place it on a table, shelf or a bookcase. Ideally around 15cm from the ceiling.
  • Don’t put it in cupboards, behind furniture or near outside doors or ventilation equipment (such as extractor fans) – this will stop it from working properly.
  • Keep the alarm away from areas of high condensation, such as bathrooms, or next to cooker hobs.
  • Test the alarm regularly, just as you would with a regular smoke alarm. Replace the batteries as soon as the low-battery signal beeps.
  • Always read and follow the manufacturer’s instructions when placing, testing and servicing the alarm. Pay close attention to any notes on its battery life, and when batteries should be replaced.

For more information on gas safety and detecting gas leaks, or what to do in a gas emergency, check out our comprehensive guides. 

How does a carbon monoxide detector work?

Carbon monoxide detectors work in a similar way to smoke or fire alarms – they sound an alarm when carbon monoxide is detected in the air. These are the 3 types of detector available:

  • Biomimetic sensor: a gel inside the alarm changes colour when it absorbs carbon monoxide. This colour change sets off the alarm. (Cheaper carbon monoxide patches which also change colour are available – but they don’t have an audible alarm, so are not recommended.)
  • Metal oxide semiconductor: the electrical resistance in the alarm is lowered when the circuit detects carbon monoxide. This change trips the alarm. 
  • Electrochemical sensor: electrodes inside a chemical solution in the alarm sense a change in electrical currents when carbon monoxide is present. This change triggers the alarm. 

Is a carbon monoxide detector the same as a smoke detector?

carbon monoxide detector poison guide placement 

Absolutely not! They detect entirely different things. A smoke alarm won’t alert you to a carbon monoxide leak, and a carbon monoxide detector won’t alert you to smoke. To be safe, you need to install both. 

Is carbon monoxide lighter than air?

Yes, carbon monoxide is actually slightly lighter than air. It can also be found within warm, rising air. For this reason, detectors should be installed at 5 feet or above.  

Do I need a carbon monoxide detector?

Yes! If you have a gas appliance in your home, you need a carbon monoxide detector. And considering two-thirds of British homes use gas, it’s likely you do, too. Around 60 people in the UK die every year from carbon monoxide poisoning, and many more suffer long-term organ damage. A detector is a vital bit of kit to protect you and your family against this risk.

Where can I buy a carbon monoxide detector?

Carbon monoxide detectors are available at most DIY stores or online. There are many different types, but go for an audible one, so you’re alerted to a leak straight away. The patch detectors, which change colour when a leak is detected, are useless if a leak occurs while you’re asleep. Reliable detectors cost £20 or more. This article by Which? offers guidance on making the right choice.  

Make sure your detector complies with the BS50291 standard, and has a British or European Kitemark.

What are the different types of carbon monoxide detectors?

There are 3 main types of carbon monoxide detectors. Don’t go cheap, go safe:

  • Sealed battery carbon monoxide detectors – this type of detector has the battery sealed inside the unit. You can’t change the battery. The alarm will beep to let you know when you need a new unit. This type of alarm can last for up to 10 years – and not needing to change the battery for 10 years is a real bonus for busy households!
  • Replaceable battery carbon monoxide detectors – the batteries will need replacing every 2 to 3 years in this kind of alarm. Although this type of detector is cheaper than sealed battery detectors, buying the replacement batteries will push the price up. These detectors last between 5 and 10 years.
  • Smart carbon monoxide detectors – if you live a smart life through your phone, this is the one for you. Not only does the alarm sound, but you also get an alert through your phone. This could be useful if you’re not at home. These alarms cost around 4 times as much as sealed battery detectors, and they’ll last between 7 and 10 years). 

How do I install my carbon monoxide alarm?

You’ve made the first important step in protecting yourself, by buying a carbon monoxide detector. But installing it in the right place is just as important. Happily, installation is a simple DIY task – it could be as easy as just putting it on a high shelf. 

Simply follow the manufacturer’s installation instructions. They should give clear instructions about placing, testing, servicing, and replacing the detector. Pay careful attention to information about battery life, and when it should be replaced. A detector with a flat battery won’t save your life. Most detectors last around 5 to 7 years, but some will do the job for as long as 10 years. 

There are some unsafe detectors out there – so do your research and make sure yours is reliable. Brands such as Fire Angel and Honeywell are reputable companies – but any that comply with BS50291 are safe to use. 

 Should I follow any safety tips for using and maintaining my carbon monoxide alarms?

The safest thing you can do is follow the manufacturer’s instructions included in the box. Keep this booklet in a safe place for future reference. Never take out the battery to use in another device – the likelihood is you’ll forget to replace it. Test the detector regularly, and replace batteries when advised to do so in the instructions. 

Learn the warning signs of carbon monoxide poisoning

Carbon monoxide poisoning symptoms are similar to flu, food-poisoning and even a hangover or tiredness. The main 6 symptoms are:

  • Headaches
  • Dizziness
  • Nausea
  • Breathlessness
  • Loss of consciousness
  • Collapse

Be alert to these signs, and learn more about protecting yourself in our newly updated blog on carbon monoxide safety

What to do if you experience symptoms of carbon monoxide poisoning

Acting quickly is vital in the case of a carbon monoxide leak. If you suspect you’re experiencing symptoms of carbon monoxide poisoning, follow these steps:

  • Turn off gas appliances
  • Open windows and doors
  • Get outside immediately 
  • Go to your nearest A&E department – they will carry out a blood or breath test.
  • Call the National Gas Emergency Number on 0800 111 999

How to be gas-safe

Taking a few simple measures can stop you being affected by carbon monoxide:

  • Read customer and safety reviews of appliances before buying a new one.
  • Make sure any engineer installing new appliances is registered with the Gas Safety Register.
  • Have gas appliances serviced every year by a Gas-Safe registered engineer to make sure they’re running correctly. If you rent your home, ask your landlord.

If you’re an OVO Energy member on our Priority Services Register, you may qualify for a free gas safety check. Call us on 0330 303 5063 to see if you’re eligible. Or check out our booklet for more information. 

For more information on carbon monoxide and how to protect yourself and your family, read our new helpful guide. 

To find out about home energy-efficiency and renewable energy options such as wind, solar, biomass, tidal or hydroelectricity, check out our handy blog posts. And for the latest on low-carbon heating ideas for your home, take a look at our guides. 

It's not only important to be safe around gas, but also around electricity. Check out our guide on electrical safety around the home, and stay safe. 

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