One of our smoke alarms started doing a short chirp every couple of hours. I assumed it was due to a low battery, so I replaced it. Didn’t help still beeping every couple hours.

I then unplugged it from the wall, took the battery out and held the test button down. Then replaced the battery and plugged it back in, still chirping every couple hours.

I then replaced the entire smoke alarm, still chirping.

THEN replaced every battery in every smoke detector in my house and still chirping every couple of hours.

Any idea what else I can try?! It’s driving me nuts

  • Are they interconnected? Is the known chirpy one just a smoke or is it also CO? Commented Dec 19, 2023 at 1:15
  • 1
    Oh, and are they hardwired for main power (with a battery backup)? Commented Dec 19, 2023 at 1:16
  • 1
    They are hardwired with battery backup. It is just a smoke no CO
    – John Ryan
    Commented Dec 19, 2023 at 1:18
  • 1
    Can you test if the "bad" one is actually getting power? If you don't have tools to test that, maybe swap it with another hardwired one in your house?
    – Olivier
    Commented Dec 19, 2023 at 1:21
  • 4
    one of the smoke alarms may have expired ... check the expiry dates
    – jsotola
    Commented Dec 19, 2023 at 5:29

1 Answer 1


Take all of the batteries out and disconnect any hardwired smoke detectors. Hold the test button to discharge them. Wait 10 minutes. If you hear any beeps after that, you missed at least one. Go find it.

Or something else is beeping: https://www.youtube.com/watch?v=Kdnnnvo7puk

Once you are done, make sure to put the batteries back in!

  • I appreciate it but I already did that. One singular detector beeping even after being replaced.
    – John Ryan
    Commented Dec 19, 2023 at 1:28
  • What the make and model number of that smoke detector?
    – longneck
    Commented Dec 19, 2023 at 1:30
  • First Alert SMI100-AC
    – John Ryan
    Commented Dec 19, 2023 at 1:45
  • Could also be one of these Commented Dec 19, 2023 at 1:47
  • 3
    @JohnRyan yes that is common for interconnected detectors. One detector may chirp to indicate another one is faulty.
    – jesse_b
    Commented Dec 19, 2023 at 2:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.