Vent, Valve & Volt
Carbon monoxide alarm going off or beeping

You can fix this

Likely cause: end of life or a malfunction

If anyone feels unwell, the alarm sounds more than one beep in a row, or it still sounds after a new battery or a new alarm, get everyone outside and call 911, as NFPA says. Kidde lists one chirp about every 30 seconds as end of life or a fault, and your manual has the final word for your model. If yours is hardwired, this one is for a licensed electrician.

Why this happens

Kidde says its CO alarms chirp every 30 seconds for end of life or a unit malfunction, that a replacement battery will not stop an end-of-life chirp, and that an alarm in end-of-life mode can no longer detect CO. First Alert lists five beeps every minute as end of life. NFPA says to replace a CO alarm according to the manufacturer's instructions or when its end-of-life signal sounds.

How to fix it

  1. Make sure nobody feels unwell. If anyone does, or the loud alarm sounds, leave and call 911.
  2. If your alarm is hardwired, do not take it off its mounting plate or disconnect its wiring. Call a licensed electrician to replace it. Until it is replaced, do not count on it to detect CO. CPSC says to have battery-operated CO alarms, or CO alarms with battery backup, on every level of the home and outside sleeping areas, so a battery-powered alarm gives you cover in the meantime.
  3. If you already replaced the batteries or the alarm and it still sounds, NFPA says to get to fresh air and call 911.
  4. Check your manual for what this pattern means on your brand. Do not rely on a pattern from another brand.
  5. Kidde says an alarm in end-of-life mode can no longer detect CO and should be replaced right away, so do not count on it to protect you until the new one is in place.
  6. Do not keep swapping batteries. Kidde says new batteries will not fix an end-of-life alarm.
  7. On a Kidde alarm that has a Peak Level button, Kidde says pressing and holding it shows an error code. Kidde says to call its Product Support at 1-800-880-6788 with the code and model details.
  8. If your alarm is battery-only, replace it with a new one and install the new one the way its instructions say. If it plugs into an outlet, unplug it and plug in a new one the way its instructions say. Do not open the alarm's case. If the new alarm still sounds, NFPA says to get to fresh air and call 911.

When to stop. If anyone feels unwell or the loud alarm sounds, get everyone outside, pets included, and call 911 from outside. That is an emergency.

If this does not fix it, tell the HVAC technician

  • The brand, model and the date on the label.
  • The chirp pattern and how often it repeats, plus any display message such as End or Err and any code.
  • Whether the alarm is battery-only, plug-in or hardwired.
  • Whether the chirping started after a power outage or a battery change.

Build the full list: what to tell the HVAC technician.

Related troubleshooters

Start this troubleshooter over

References (every fact above comes from one of these pages)
  1. Kidde: Why is my carbon monoxide alarm beeping or chirping?
  2. Kidde: Carbon monoxide detector replacement FAQs
  3. Kidde: Is my carbon monoxide digital alarm at end of life?
  4. Kidde: How to retrieve the error code on a carbon monoxide alarm
  5. Kidde: Carbon monoxide or combination alarm battery replacement
  6. First Alert: Why is my carbon monoxide detector beeping?
  7. NFPA: Educational messages desk reference, chapter 3, carbon monoxide (PDF)
  8. CPSC: Carbon monoxide

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