What is Carbon Monoxide?

Carbon monoxide (CO) is an extremely dangerous gas that has no colour, smell or taste and cannot be detected by the human senses. It is produced when fossil fuel (gas, oil, coal, wood, etc.) is not burnt properly and when inhaled it combines with the haemoglobin in red blood cells and reduces the oxygen-carrying capabilities of the body.

Why is Carbon Monoxide So Dangerous?

Because carbon monoxide has no colour, smell or taste it is completely invisible and undetectable to human senses. The symptoms of carbon monoxide poisoning can also be easily mistaken for flu making it extremely dangerous and hard to recognise.

Inhaling carbon monoxide reduces the oxygen-carrying capability of the blood and leaves vital organs and tissue starved of oxygen. Every year in the UK, around 4000 people visit an A&E department with suspected carbon monoxide poisoning and around 60 people die as a direct result of exposure to carbon monoxide. Many more people die as a result of strokes and respiratory illnesses made worse by inhaling low levels of CO over prolonged periods.

Sources of Carbon Monoxide

Fuel-burning appliances should be maintained regularly but, no matter how rigorous maintenance schedules are, appliances may become damaged and stop functioning properly at any time, creating a source of carbon monoxide. The most common sources of carbon monoxide are:


Be aware of flames burning orange or yellow instead of intense blue, and pilot lights that frequently go out.


Watch out for dark, sooty stains on and above your cooker and lazy yellow or orange flames on your hob.


Fires becoming difficult to light could indicate that fuel is not burning correctly and that CO is being produced.

Wood Burners

Ensure you service your wood-burning appliances regularly and always use engineers approved by HETAS.


Smouldering coal produces high levels of carbon monoxide. Never use a barbecue inside or in an enclosed space.

Gas / Paraffin Heaters

Ensure your room has adequate ventilation and that your heater is well-maintained and regularly serviced.

Portable Generators

Portable generators should be maintained and serviced regularly. Always use them outdoors or in a well-ventilated space.


Carbon monoxide can seep through walls, be aware of neighbouring properties and ensure you have an audible CO alarm.


The difference between CO and CO2

Carbon monoxide has the chemical symbol of CO and is often mistaken for carbon dioxide, which has a chemical symbol of CO2. While the two gases are similar in terms of molecular structure, there is a big difference between how the human body interacts with them and how dangerous they can be to your health.

Carbon Dioxide (CO2)

Carbon dioxide has the chemical symbol of CO2 and consists of 1 x carbon atom and 2 x oxygen atoms. It occurs naturally in the Earth's atmosphere as a trace gas and is produced as a by-product of the human respiratory system. Carbon dioxide is usually odourless, but at high levels is known to have a very sharp acid smell.

Carbon Monoxide (CO)

Carbon monoxide has the chemical symbol of CO and consists of 1 x carbon atom and 1 x oxygen atom. It is produced when there isn't enough oxygen in the combustion process to form carbon dioxide. Carbon monoxide is colourless, odourless, and tasteless but is very poisonous to humans and animals.


Useful Contact Numbers

If you experience a carbon monoxide incident or need more help and advice about carbon monoxide safety, please use the following contact details.

Gas Appliances

0800 111 999


Oil & Biofuel Appliances

01473 626 298


Solid Fuel Appliances

01684 278 170


Carbon Monoxide Info

01507 462 176

Contact Us



Reviewed: 22/06/2023 (doc:542 V1.1). Our articles are reviewed regularly. However, any changes made to standards or legislation following the review date will not have been considered. Please note that we provide abridged, easy-to-understand guidance. To make detailed decisions about your fire safety provisions, you might require further advice or need to consult the full standards and legislation.

Carbon Monoxide Poisoning

Many people are unaware of the devastating effects of carbon monoxide poisoning. Carbon Monoxide has no colour, smell or taste and cannot be detected by the human senses. It is extremely dangerous, binding itself to the haemoglobin in red blood cells and preventing them from transporting oxygen around the body.


Estimated Number of Deaths Every Year

According to statistics released by the Office for National Statistics, throughout England and Wales, there are an average of over 60 deaths every year due to accidental exposure to carbon monoxide - up to 45% of which occur in the home.

Source: ONS, User Requested Data, Refs 006780, 007476 & 009122


People Treated for CO Poisoning Every Year

Figures from the Department of Health and Social Care show that there are around 4000 cases of carbon monoxide poisoning treated in A&E Departments across England each year - even mild cases can exacerbate existing conditions such as respiratory illnesses, leading to fatalities.

Source: Department for Health and Social Care


Number of People Hospitalised Every Year

According to the Chief Medical Officer (CMO) for England, around 200 per year are hospitalised in England and Wales as a result of accidental carbon monoxide poisoning.

Source: Department for Health and Social Care


Percentage of UK Households with a CO Alarm

A study of more than 27,000 properties by the Liverpool John Moores University, supported by the Merseyside and West Midlands Fire Services, found that less than 10% of homes have a single carbon monoxide alarm to protect occupants from this deadly gas.

Source: Liverpool John Moores University

Share Your CO Story

We share real-life stories of our customers to help raise awareness of the dangers of carbon monoxide. Hearing about a near miss can sometimes prompt you to think about your own situation and may highlight a risk within your own home.

If you share your CO story with us, and it is posted on our website, we will give you a free carbon monoxide alarm. Help us spread the word and save lives.


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