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uk Home & property emergencies

What to do if…
your carbon monoxide detector is beeping, chirping, or showing a fault signal

Produced and maintained by PanicStation.org Published: Last reviewed: Editorial policy UK guide

Short answer

Treat the signal as potentially serious until everyone is in fresh air. If anyone has severe symptoms, collapses, has trouble breathing, or you think there is immediate danger, call 999; if gas could be involved, call the gas emergency number from outside.

Do not do these things

  • Do not ignore it, sleep on it, or assume it is just a glitch if you are unsure.
  • Do not keep using a boiler, gas cooker, fire, log burner, portable heater, or any appliance that burns fuel.
  • Do not stay inside to air the property out; only open doors or windows if you can do it on the way out without delaying leaving.
  • Do not silence, reset, or remove the alarm and then carry on as normal.
  • Do not re-enter after a possible carbon monoxide alarm unless emergency services, the gas emergency service, or a qualified professional tells you it is safe.

What to do now

  1. Get everyone, including pets, into fresh air first. Go outside or to another place where you can breathe clean air.
  2. Check quickly for symptoms. Headache, dizziness, nausea, confusion, unusual tiredness, breathlessness, collapse, or more than one person feeling unwell in the same place are warning signs.
    • If someone collapses, has severe symptoms, has trouble breathing, has a seizure, or you think there is immediate danger: call 999.
    • If someone feels unwell or worried after possible exposure but it is not an immediate emergency: call NHS 111, contact a GP, or seek urgent medical advice.
  3. If gas could be involved, call the gas emergency number from outside.
    • Great Britain: 0800 111 999 for the National Gas Emergency Service, available 24 hours a day.
    • Northern Ireland: 0800 002 001 for the Northern Ireland Gas Emergency Service, available 24 hours a day.
    • If the appliance uses LPG from a cylinder or tank, follow the gas emergency service’s advice and check the supplier or tank emergency details when it is safe to do so.
  4. Leave fuel-burning appliances off. Do not relight, restart, or test a boiler, cooker, heater, fire, stove, generator, or similar appliance while there is any chance this was a carbon monoxide warning.
  5. Only once you are safely away from possible exposure, check what the alarm is trying to tell you.
    • Look at the alarm label for the model, then check the display, LED pattern, beeps, or message against the manufacturer’s instructions.
    • If the signal is clearly low battery and the alarm has replaceable batteries, replace them following the manufacturer’s instructions.
    • If the signal says fault, error, sensor fault, or end-of-life, or the alarm still does not test correctly after the instructed battery step, replace the whole alarm promptly.
  6. Arrange a qualified check before normal use if there is any doubt.
    • For gas appliances, use a Gas Safe registered engineer.
    • For solid fuel appliances, ask for an appropriately qualified solid fuel professional; in Great Britain this may be a HETAS registrant.
    • For oil appliances, check an OFTEC registered technician or another appropriately qualified oil professional.
  7. If you rent, tell your landlord or agent immediately. Say the carbon monoxide alarm is showing a fault or warning signal, say whether anyone felt unwell, and ask for the alarm and any relevant appliance to be checked or replaced.
  8. Do not go back to normal use just because the alarm has stopped. If it may have been a carbon monoxide alarm, wait for advice from the gas emergency service, emergency services, your landlord, or a qualified professional before using the appliance again.

What can wait

  • You do not need to prove whether there was carbon monoxide right now.
  • You do not need to decide who is responsible for the alarm or appliance while you are still dealing with the immediate risk.
  • You do not need to research alarm standards, repair the alarm yourself, or do DIY work on a boiler, heater, stove, flue, or chimney.
  • You do not need to collect belongings before leaving if anyone is unwell or the alarm may be warning of carbon monoxide.

Important reassurance

It is common to feel unsure because alarms can use different beeps, lights, and messages for low battery, fault, end-of-life, and carbon monoxide detection. If you cannot confidently tell which it is, leaving first and checking the instructions from fresh air is a sensible first step.

Scope note

These are first steps only, to help you stay safe and avoid a bad decision in the moment. Later decisions about repairs, replacement, landlord duties, medical follow-up, or appliance safety may need specialist help.

Important note

This is general information, not professional safety, medical, legal, housing, or technical advice. If anyone is unwell, the alarm may have detected carbon monoxide, or a fuel-burning appliance may be involved, get urgent help and professional checks.

Additional Resources

Closely connected guides that may be useful during the same situation or its immediate aftermath.

About this guide

This guide was produced and is maintained by PanicStation.org using its published editorial process. Official and specialist sources are checked where relevant, and AI-assisted tools may be used for drafting, organisation, and consistency checks. The site operator remains responsible for publication, revision, and removal decisions.

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