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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 USA guide

Short answer

Move everyone to fresh air first. From outside, call 911 if the alarm may be indicating carbon monoxide, if you are not sure what the signal means, or if anyone feels unwell.

Do not do these things

  • Do not assume a warning is harmless just because it is “only chirping” if you are unsure what it means.
  • Do not silence, reset, or unplug the alarm and keep using a furnace, water heater, fireplace, stove, generator, vehicle, or fuel-burning heater.
  • Do not run a generator, grill, camp stove, pressure washer, or vehicle in a home, basement, garage, or near windows or doors.
  • Do not stay inside to ventilate. If it is easy to do as you leave, open a door or window on the way out.
  • Do not keep going back inside to investigate if anyone has a headache, dizziness, weakness, nausea, vomiting, confusion, chest pain, fainting, or unusual sleepiness.

What to do now

  1. Get everyone, including pets, into fresh air immediately. Go outdoors or to an open-air area away from the building.
  2. Treat a possible CO alarm as an emergency. If the unit says “CO,” gives a continuous alarm, repeats a warning pattern you do not understand, or anyone feels unwell, call 911 from outside.
  3. Do not re-enter until it is cleared. If you called 911 or the alarm may have indicated carbon monoxide, wait for emergency responders to say it is safe before going back inside.
  4. If you smell gas, treat that as a separate urgent hazard. Leave first, then call 911 or your gas utility’s emergency line from outside.
  5. Only troubleshoot the detector after you are safe and not treating it as an active CO alarm.
    • Read the label on the unit and the manufacturer’s instructions for the exact light, screen, or beep pattern.
    • Replace the batteries if the model uses replaceable batteries.
    • Press the test button only as the instructions say. A test button can show that the alarm circuit works, but it does not prove the air is safe.
    • If the unit shows end of life, still shows a fault, will not test, or you cannot confirm what the signal means, replace the whole CO alarm promptly.
  6. Do not restart fuel-burning equipment after a possible CO event until it has been checked. Ask emergency responders, your utility, landlord, or a qualified technician what needs inspection before using the furnace, water heater, fireplace, wood stove, gas appliance, oil appliance, propane appliance, chimney, vent, or generator again.
  7. If anyone feels ill, get medical help. Tell the 911 dispatcher or medical staff that carbon monoxide may be involved.

What can wait

  • You do not need to identify the exact source right now.
  • You do not need to keep checking the alarm pattern from inside the home.
  • You do not need to decide on repairs, replacement equipment, landlord issues, or insurance claims in this moment.

Important reassurance

It is normal to feel unsure because chirps, fault lights, low-battery signals, and alarm sounds vary by model. When you are not sure, stepping outside and treating it as a possible carbon monoxide risk is a reasonable first move.

Scope note

These are first steps only. Later decisions about the alarm, appliances, repairs, rental housing, insurance, or medical follow-up may need help from emergency responders, a qualified technician, your utility, a clinician, or another appropriate specialist.

Important note

This is general safety information, not medical advice, legal advice, professional home inspection advice, or a substitute for local emergency instructions. If the alarm may indicate carbon monoxide, if anyone feels unwell, or if you are not sure what the signal means, call 911 from outside and follow their instructions.

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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