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us Home & property emergencies carbon monoxide alarm fault • co detector error • co alarm warning light • carbon monoxide detector chirping • co alarm beeping intermittently • co alarm low battery • co alarm end of life signal • co detector malfunction • co alarm false alarm worry • co alarm not working • co alarm won’t test • carbon monoxide alarm troubleshooting • unsure if co is present • fuel burning appliance concern • furnace water heater co concern • gas heater co risk • generator carbon monoxide worry • move to fresh air now

What to do if…
your carbon monoxide detector shows a fault or warning signal and you’re not sure it’s working

Short answer

Move everyone to fresh air first, because you can’t safely “troubleshoot” a possible CO situation from inside. Once outside, call 911 if the alarm indicates CO or anyone feels unwell, then deal with the detector and any appliances.

Do not do these things

  • Do not assume a warning is harmless just because it’s “only chirping” if you’re unsure what it means.
  • Do not silence/reset the alarm and keep using the furnace, water heater, fireplace, stove, or any fuel-burning heater.
  • Do not run a generator, grill, camp stove, or vehicle in/near the home, garage, or near windows to “test” anything.
  • Do not stay inside to ventilate. If you can, open doors/windows as you leave.
  • Do not re-enter repeatedly to investigate if anyone feels dizzy, nauseated, confused, or unusually sleepy.

What to do now

  1. Get everyone (and pets) into fresh air immediately. Go outdoors or to an open-air area.
  2. Treat “CO alarm / CO message / continuous alarm / not sure what it means” as an emergency. From outside: call 911.
    If anyone has symptoms like headache, dizziness, weakness, nausea/vomiting, confusion, chest pain, or fainting: call 911.
  3. Do not re-enter until cleared if you called 911 or the alarm indicated CO. Wait for emergency responders’ instructions/permission before going back inside.
  4. If it’s clearly a device trouble/maintenance signal (not a CO alarm) and nobody is unwell:
    • If you smell gas, leave and call your gas utility’s emergency line (or 911 if you can’t reach them quickly).
    • Otherwise, proceed to detector maintenance (next step) and plan an appliance check if you have fuel-burning equipment.
  5. Troubleshoot the detector once you’re safe (and not treating it as an active CO alarm):
    • Read the label on the unit for the model and confirm what the light/beep pattern means.
    • Replace the batteries if applicable.
    • Use the test button after battery replacement (per the unit’s instructions).
    • If it signals end of life or still shows a fault after battery change/test, replace the entire alarm promptly.
  6. Before returning to normal use, get appliances checked if there’s any doubt. A qualified technician should inspect the furnace, water heater, fireplace/wood stove, or any gas/propane/oil appliance if the alarm indicated CO, you had symptoms, or responders advised it.

What can wait

  • You do not need to identify the exact source immediately—fresh air and the right help come first.
  • You do not need to keep re-checking the alarm pattern from inside the home.
  • You do not need to make big decisions (repairs vs. replacement, landlord disputes, insurance claims) right now.

Important reassurance

It’s normal to feel uncertain because “chirps,” “fault lights,” and “alarm sounds” can mean different things depending on the model. When you’re not sure, treating it like a real CO risk first is the safest choice.

Scope note

These are first steps to reduce immediate risk and prevent a bad call under stress. A professional inspection may still be needed to confirm the home is safe and the alarm is functioning correctly.

Important note

This is general safety information, not medical advice or a home inspection. If anyone feels unwell, if the alarm indicated CO, or if you’re not sure what the signal means, call 911 and follow local emergency instructions.

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