Carbon Monoxide Safety: The Complete Home Guide

Carbon monoxide (CO) is a poisonous gas produced when fuels like gas, oil, coal and wood do not burn fully. You cannot see it, smell it or taste it — which is exactly what makes it so dangerous. According to UK government and NHS figures, accidental carbon monoxide poisoning causes around 40 deaths and roughly 4,000 A&E visits in England every year, and almost all of it is preventable. This guide explains how to keep your home safe.

As a Gas Safe registered engineer working across Wolverhampton, Walsall and the West Midlands, carbon monoxide safety is the single most important part of my job. The good news is that protecting your home comes down to a few simple, reliable steps.

What Is Carbon Monoxide and Why Is It So Dangerous?

When a gas appliance burns fuel correctly, it produces mostly carbon dioxide and water vapour, which are safely carried outside through the flue. If the appliance is faulty, badly installed, or poorly ventilated, it can burn incompletely and produce carbon monoxide instead.

Once inhaled, CO enters your bloodstream and prevents your red blood cells from carrying oxygen around your body. At low levels it causes headaches and sickness; at high levels it can cause collapse, loss of consciousness and death — sometimes within minutes. Because it has no smell, people are often overcome before they realise anything is wrong.

The Warning Signs of Carbon Monoxide Poisoning

The NHS lists the main symptoms of carbon monoxide poisoning as:

• Headache — often the first and most common sign
• Dizziness and feeling weak
• Feeling or being sick
• Tiredness and confusion
• Chest and muscle pain
• Shortness of breath

These are easily mistaken for flu, tiredness or a hangover. The tell-tale difference is the pattern: CO symptoms tend to ease when you leave the property and come back when you return, and other people and pets in the home often feel unwell at the same time. If you notice that pattern, treat it as a warning. You can read more in our detailed guide to carbon monoxide symptoms.

Where Does Carbon Monoxide Come From in the Home?

Any appliance that burns fuel can produce CO if it is faulty or poorly maintained. The most common household sources are:

• Gas boilers and water heaters
• Gas fires, back boilers and open flue appliances
• Gas cookers and ovens
• Wood, coal and gas open fires
• Wood-burning and multi-fuel stoves
• Paraffin and portable gas heaters
• Blocked or damaged chimneys and flues

Never bring a barbecue, camping stove or portable generator indoors or into a tent, and never run a car or petrol engine in an enclosed space such as a garage — these are frequent causes of serious poisoning, especially in the colder months.

How to Protect Your Home From Carbon Monoxide

Three habits prevent the overwhelming majority of CO incidents:

1. Fit audible CO alarms. Buy alarms marked to the British and European standard BS EN 50291, and fit one in every room with a fuel-burning appliance. A CO alarm is not a substitute for servicing, but it is your last line of defence.

2. Service appliances every year. Have your boiler, fire and other gas appliances checked annually by a Gas Safe registered engineer. During a service we check combustion, the flue and ventilation, and confirm the appliance is not producing dangerous CO. You can book our annual boiler service across the West Midlands.

3. Keep rooms ventilated and flues clear. Never block air vents or bricks, and have chimneys swept and flues checked regularly. Appliances need a good air supply to burn safely.

Where to Fit a Carbon Monoxide Alarm

Placement matters. For each fuel-burning appliance, follow the manufacturer's instructions and this general guidance:

• Fit the alarm at head height, ideally on a wall
• Position it roughly 1 to 3 metres horizontally from the appliance
• Keep it away from windows, doors, extractor fans and air vents that could draw CO away
• Do not put it right next to the appliance, or hidden inside a cupboard or behind furniture
• Test it regularly using the test button, and replace it at the end of its stated lifespan (usually 5 to 10 years)

What to Do If Your CO Alarm Goes Off

If your carbon monoxide alarm sounds, act immediately:

• Stop using the appliance you think is responsible
• Open doors and windows to let fresh air in
• Get everyone out of the property into fresh air
• Call the free National Gas Emergency line on 0800 111 999 (24 hours a day)
• Seek medical advice — call NHS 111, or 999 if anyone is seriously unwell
• Do not go back inside until you are told it is safe and the appliance has been checked by a Gas Safe registered engineer

Landlords and Carbon Monoxide: The Law

Since the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 came into force on 1 October 2022, landlords in England must fit a carbon monoxide alarm in any room used as living accommodation that contains a fixed combustion appliance — such as a gas boiler or a log burner. Gas cookers are the one exception and do not trigger the requirement.

Landlords must also ensure alarms are working at the start of each new tenancy, and repair or replace them once told they are faulty. This is on top of the annual gas safety inspection — see our guide to CP12 certificates for the full landlord obligations.

Frequently Asked Questions