Are you concerned about the dangers of carbon monoxide from your boiler?

Carbon monoxide kills, so it’s a very good concern to have. But what causes it, and what should you look out for?

I’ve been asked many a time to attend to properties which have been affected by carbon monoxide, and some of them have potentially been very dangerous.

Below, I’m going to tell you the main causes of carbon monoxide in the home, and what you can do to protect yourself.

What is carbon monoxide?

Carbon monoxide is a highly poisonous and potentially lethal gas. Carbon monoxide may not always kill you, but it could lead to brain damage and long-term health problems.

You can’t see or smell carbon monoxide, which is why it’s absolutely essential to take precautionary measures, such as installing carbon monoxide detectors in your home.

What causes carbon monoxide?

The presence of carbon monoxide is caused by malfunctioning, incorrectly fitted or badly maintained gas appliances. It can also be caused by blocked vents, chimneys or flues.

I once received a call to a rented property with an open-flued boiler, where tenants often felt tired and complained of headaches. Upon inspection, it was found that the tenants had actually covered up the air vent in the window to stop cold drafts.

This was soon rectified by unblocking the vent, and fitting a carbon monoxide detector. However, after having stressed the dangers of the current set-up to the landlord, he changed the boiler to a room sealed appliance three months later.

Open-flued boilers

Many old boilers have open flues, which means they take the air for combustion from the room. If you have an open-flued boiler, you’ll notice you probably have air vents in the floor or window to provide fresh air.

If the boiler can’t get the air, natural thermal convection cannot occur, so instead of fumes going up the chimney flue, it spills lethal carbon monoxide into the room. As a result, you will be vulnerable to carbon monoxide poisoning.

The symptoms of carbon monoxide poisoningo

Carbon monoxide poisoning symptoms can feel like you’re simply overtired, coming down with the flu, a virus, or food poisoning. Not everyone recognises the symptoms, making this especially dangerous.

Other signs to look for include:

  • Only experiencing symptoms when you’re at home
  • Your symptoms mysteriously vanish when you’re outside
  • Others in your home (including pets) also experience symptoms at the same time

What to do if you suspect carbon monoxide

If you think there is a chance there may be carbon monoxide leaking into your home, you must:

  • Open the doors and windows, turn off gas appliances and go outside
  • Consult a doctor or go to a hospital. They can perform a blood or breath test to be sure
  • If it is an emergency, call the Gas Emergency Helpline
  • Get the appliance checked immediately by calling a Gas Safe registered engineer
  • Fit carbon monoxide detectors in rooms with gas appliances and flues

Carbon monoxide detectors

It’s important to fit carbon monoxide detectors in any rooms that contain a gas appliance or flue. This is because they give you the eyes and ears to a silent killer you can’t see, hear or taste.

They have saved many lives, and from October 2013 it is mandatory to fit one in the same room whenever a gas appliance is fitted in Scotland.

You can purchase carbon monoxide detectors from all DIY stores, plumbers’ merchants and electrical merchants, along with stores such as Tesco. There is NO excuse not to have one.

TIP: Just like smoke detectors, carbon monoxide detectors are battery operated and should be checked, and batteries changed, annually.

Don’t risk it

These days, people are more aware of the dangers of carbon monoxide, and detectors are readily available, along with free help and advice from the Gas Safe Register. Never think you are wasting someone’s time – if you’re ever in doubt, call out and have an expert check it’s safe.

Don’t take chances; always service appliances when due, and don’t store clothing or clothes horses in cupboards with open-flued appliances. There will be warning notices in these cupboards, so do not ignore them.


If you’re concerned about carbon monoxide in your home, you should get it checked out immediately by a Gas Safe registered heating engineer. Carbon monoxide is incredibly dangerous, as you can’t see it, smell it or taste it.

The symptoms of carbon monoxide can be difficult to spot, as they can seem like you’re overtired, have the flu, or are suffering from food poisoning. If these symptoms vanish when you go outside, call a professional to check your gas appliances.

Ensure you have carbon monoxide detectors fitted in rooms where there is a gas appliance or flue. Check the batteries regularly and change them once a year. You can purchase detectors from a variety of places, including supermarkets such as Tesco.