Carbon Monoxide Alarm Going Off? What to Do Now

Carbon monoxide (CO) has no smell, no colour and no taste. A working alarm is the only way to know it’s there, so always take it seriously — even if everyone feels fine.

🔔 Real Alarm, or Just a Beep?

Sound patterns differ between makes, so check the manual or the label on the back. If you’re not sure, treat it as a real alarm. CO alarms last 7 or 10 years depending on the model — the replace-by date is printed on the alarm.

⏸️ The Alarm Stopped — Is It Safe Now?

Not necessarily. Opening the windows lets the CO escape, so the alarm may go quiet — but whatever made it is still there and will start again when you close up and switch back on. Still call 0800 111 999 and don’t use the appliance until it’s been checked. If the alarm goes off again later, repeat the steps.

Never silence or take down a CO alarm without finding out why it went off.

🩺 Symptoms of Carbon Monoxide Poisoning

• Headache, dizziness, feeling weak, tiredness or confusion
• Feeling or being sick
• Chest and muscle pain, shortness of breath
• Face turning hot and red, or loss of vision

They’re easy to mistake for flu, food poisoning or a hangover. A clue is that they ease when you’re away from home and come back when you return, or that several people (or pets) in the home feel unwell at the same time.

If you think anyone has been exposed, get medical advice before going back in: call NHS 111, or 999 if they have trouble breathing, chest pain, sudden confusion or have collapsed. Don’t drive yourself to hospital.

🚒 What Happens Next

1. The emergency engineer from your local gas network comes out, checks for CO and makes the property safe — usually by turning off the faulty appliance and leaving a warning notice on it.
2. A Gas Safe registered engineer then finds out why the appliance was producing CO — often a blocked flue or vent, poor combustion, or a fault inside the appliance — repairs it, and tests it before it’s used again.

With FE Maintenance, an emergency call-out is from £99, and you get a fixed price for the repair before any work starts — no VAT added. We take emergency gas call-outs Monday to Friday, 8am–8pm, aiming to be with you within 2–4 hours. At other times, call 020 8445 1303 and we’ll tell you if we can come.

🔍 What Causes Carbon Monoxide at Home?

CO is made when fuel doesn’t burn properly. Common causes:

• A boiler, gas fire or cooker that is faulty or hasn’t been serviced
• A blocked or damaged flue or chimney
• Air vents that have been blocked or covered
• A barbecue or camping stove used indoors — even after it has gone out
• A car or generator running in an attached garage

📍 Getting Your CO Alarms Right

• Fit a CO alarm in every room with a gas boiler, gas fire, wood burner or other fuel-burning appliance. In rented homes, landlords must do this by law (gas cookers are excluded).
• Follow the maker’s instructions — typically at least 1.5 metres from the appliance, and not right next to windows, doors or vents.
• Press the test button regularly — once a month is a good habit.
• Replace the alarm by the date printed on it.

The full rules for landlords: smoke and carbon monoxide alarm requirements.

🏠 Renting? Tenants and Landlords

• Tenants: follow the same steps and call 0800 111 999 first. Then tell your landlord or letting agent straight away. Don’t use the appliance until it has been checked.
• Landlords: arrange a Gas Safe engineer quickly and keep a record of the repair. A yearly gas safety check tests every gas appliance and flue, and we check the CO alarm works at the same visit.

🛡️ Preventing Carbon Monoxide

• Have your boiler and gas appliances serviced every year by a Gas Safe registered engineer — boiler service from £80.
• Never block air vents, and keep flues and chimneys clear.
• Watch for warning signs on gas appliances: a lazy yellow or orange flame instead of a crisp blue one, black marks or soot around the appliance, or a pilot light that keeps going out.
• Never use a barbecue or camping stove indoors.