Why is my carbon monoxide alarm beeping?
By Azzeddine Kebbi, NAPIT-registered electrician and director of Kebbi Electrical Services · Updated 10 November 2026
A loud, repeating alarm means carbon monoxide has been detected: get everyone outside and call 0800 111 999. A single chirp every minute or so usually means a low battery or an alarm at the end of its life. Here is how to tell the difference.
If the full alarm is sounding
- Do not assume it is a false alarm. Carbon monoxide has no smell or colour.
- Open doors and windows and turn off fuel-burning appliances if it is safe to.
- Get everyone, including pets, outside.
- Call the National Gas Emergency Service on 0800 111 999.
- If anyone has a headache, dizziness, sickness or breathlessness, get medical help.
What the beep usually means
Loud, repeating alarm
Carbon monoxide detected. Follow the steps above.
Single chirp every minute or so
Low battery on most models. Replace it, or the alarm if the battery is sealed.
Chirp plus a flashing light
Often the end-of-life warning. Check the replace-by date on the alarm.
Not sure which?
Patterns differ between makers. The label or manual on the alarm lists them.
Alarm patterns vary by brand, so always check the instructions for your model.
Keeping your CO alarm working
- Press the test button once a month.
- Replace the whole alarm by the date printed on it, usually 7 to 10 years.
- Have one in every room with a boiler, wood burner, open fire or other fuel-burning appliance.
- Get gas appliances serviced by a Gas Safe registered engineer. An alarm is a backup, not a replacement for servicing.
Common questions
What do I do if my carbon monoxide alarm goes off?
Treat it as real. Open doors and windows, turn off gas, oil or solid-fuel appliances if you can, get everyone outside and call the National Gas Emergency Service on 0800 111 999. Get medical help if anyone feels unwell.
Why is my carbon monoxide alarm chirping?
A short chirp every minute or so usually means a low battery or that the alarm has reached the end of its life. Check the label: most makers use a different pattern for each.
How long do carbon monoxide alarms last?
Most last between 7 and 10 years, depending on the model. The replace-by date is on the alarm. When it reaches that date, replace the whole unit.
Can a smoke alarm detect carbon monoxide?
No. A standard smoke alarm does not detect carbon monoxide. You need a separate CO alarm, or a combined smoke and CO alarm.
Where should a carbon monoxide alarm go?
In the room with the fuel-burning appliance, such as a boiler, wood burner or open fire. Follow the maker's instructions for the exact distance from the appliance.
Do landlords have to fit carbon monoxide alarms?
In England, private and social landlords must fit a carbon monoxide alarm in any room used as living space that has a fixed combustion appliance, gas cookers excepted, and repair or replace alarms when told they are faulty.
Need alarms fitted or checked?
See our fire alarm installation in Bristol, or get in touch about alarms and electrical safety in your home.