I have a hardwired smoke alarm that beeps even when I take the batteries out, unplug it from the outlet, and remove its cellularies. I was wondering if this is possible and if so, how long can they beep for? I heard a story of one that beeped for 8 years without batteries or an outlet.

  • 8 years without batteries or connecting to an outlet? I am really skeptical of that. Are you sure you don't have something else beeping? Noises like these beeps can be surprisingly hard to pinpoint. Nov 16, 2020 at 21:07
  • Well mine was only a couple of hours then I replaced the batteries, it was the story that was 8 years
    – HuCooper
    Nov 16, 2020 at 21:26
  • "Cellularies"? What's that?
    – isherwood
    Nov 16, 2020 at 21:52
  • "Hard wired" and "unplug from outlet" don't jive. A hardwired smoke detector is mounted to a box on the wall/ceiling and has house wiring going directly into the back of it - you should never see this wiring unless you've used a screwdriver. A plug-in smoke detector (is there really such a thing) would be plugged into an outlet and would have a cord running down the wall, or there would be an outlet high up on the wall or the ceiling. Please edit your post to include pics of the detector in question showing the label with model #.
    – FreeMan
    Nov 16, 2020 at 23:30
  • Maybe it's handwired, is that a thing? I just know we had it disconnected from the wall and the batteries out and i heard from some that it was still possible it could beep
    – HuCooper
    Nov 16, 2020 at 23:37

1 Answer 1


Yes if you remove all power it can beep a few times from stored energy in the detector. But not 8 years. 8 seconds, maybe. I never heard of the fire code ever allowing "plug in" smoke detectors, though. They are supposed to be permanently mounted (or rather mounted well enough to be difficult for the average conehead to mess with.)

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