Carbon Monoxide: The Silent Killer

Where it comes from, how it feels and how to stop it

6 minBeginnerUpdated 2026-10-23 Carbon Monoxide: The Silent Killer

You will learn

Name the common sources of carbon monoxide in a home, a garage and a tent
Recognise the symptoms and the warning pattern of CO poisoning
Act fast in an emergency and prevent it with an alarm and maintenance

⚠️ If a CO alarm sounds or you suspect poisoning, get everyone into fresh air at once, do not go back inside, and call 112.

⚠️ Never use a generator, charcoal, a barbecue or a fuel heater indoors, in a garage or in a tent.

⚠️ Anyone with symptoms needs medical assessment, even if they feel better outside.

Where it comes from

Carbon monoxide, CO, is a gas made whenever fuel burns without enough air. You cannot see it, smell it or taste it, which is why it kills people in their sleep every winter. Anything that burns fuel can produce it: wood stoves and fireplaces with a blocked or leaking flue, gas heaters, gas boilers and water heaters, generators, cars left running in a garage, a charcoal barbecue brought indoors to keep warm, and camping stoves or heaters used inside a tent or caravan. Old or badly maintained appliances and poor ventilation make it far more likely. Rural houses heated by wood and bottled gas, closed up tight against the cold, are exactly where it happens.

How it feels

Early CO poisoning feels like flu or tiredness: headache, dizziness, nausea, weakness and confusion. Higher levels bring vomiting, chest pain, collapse and loss of consciousness, and death can follow within minutes at very high levels. Because the signs are vague, look for the pattern instead. Several people in the house feel ill at the same time. Pets are sluggish or sick too. Symptoms are worse in one room or when a particular appliance is on, and they ease when you go outside or leave the house for the day. Anyone asleep or drunk can die without ever waking. Babies, older people, pregnant women and anyone with heart or lung disease are at greatest risk.

💡 Headache that lifts when you leave home and returns when you come back is a warning sign. Take it seriously.

What to do if you suspect it

Act immediately; do not stop to investigate. Get everyone, including pets, out into fresh air at once. On your way out, open doors and windows only if you can do it quickly without delaying your escape, and switch off the appliance only if it is right in your path. Do not go back inside for anything. Call the emergency number, 112 in Europe, and say you suspect carbon monoxide poisoning. Anyone with symptoms needs medical assessment even if they start to feel better in the fresh air, because CO can cause lasting harm to the heart and brain. Do not use the appliance again until a qualified technician has checked it.

Prevention: alarm, sweep, never indoors

Fit a carbon monoxide alarm that meets the European standard EN 50291, near sleeping areas and in every room with a fuel-burning appliance, following the maker's instructions for placement. Test it monthly with the button and replace it when it reaches the end of its life. A smoke alarm does not detect CO. Have chimneys and flues swept at least once a year, and gas appliances serviced by a qualified technician. Never block air vents, even in winter. Never run a generator indoors, in a garage or near open windows and doors. Never bring a charcoal barbecue or grill indoors or into a tent, even when it seems to have gone out, and never run a car engine in a closed garage.

💡 Put a CO alarm in your camping and caravan kit as well. Tents are small spaces that fill fast.

Check yourself

How can you detect carbon monoxide without an alarm?

CO is invisible and odourless. Only an alarm can warn you reliably.

Which pattern most strongly suggests CO poisoning?

Several people or pets ill at once, and better when away, is the classic warning pattern.

You suspect CO in the house. What comes first?

Get out first. Open doors and windows only on the way out, never go back in, and call 112.

Where is it safe to use a charcoal barbecue?

Charcoal produces large amounts of CO, even while cooling. It belongs outdoors only.

Try it for real: Make your home CO-safe

List every fuel-burning appliance in your home, garage, caravan or camping kit
Check you have a working CO alarm near sleeping areas and each appliance, and press the test button
Book or note the date of the next chimney sweep and appliance service
Agree with your household: if the alarm sounds, everyone goes straight outside