A few months ago, I started hearing a quiet mysterious beep around every 1 minute in our basement. We could not find it after an afternoon of standing in different spots and we were 99% sure it was coming from the inside ceiling. It wasn't bad and it didn't bother people too much so we hoped it would stop. Just two days ago, I started hearing a loud beep each minute accompanying the softer beep like a dying smoke detector in the spot where I have a wired smoke detector. I assumed there was something wrong with the smoke detector, but when I pulled it out and took it to another room, the detector did not beep. However, the loud beep is still coming from the same area as the smoke detector with no detector plugged in. This sound appears to be in the ceiling.

Any ideas what this could be? Is anyone aware of any systems out there where there is an overall backup battery to a wired system? Or are there wired smoke alarm systems where there some type of detector if something in the wired system is not wired correctly? How would you solve this if it's in a drywall covered ceiling?

To be clear:

  • Every minute I hear a loud chirp like a dying smoke detector, followed by the original soft beep about 10 seconds later. This never stops.
  • I have whole house wired smoke detector system. 4 are Kidde and the rest are old ones I need to replace.
  • I haven't touched the alarms in weeks, this just started happening.
  • After many trips around the room to find the location, both sounds are emanating from the ceiling, and access would require cutting into it.

Edit: Thanks for the help everyone. I'm still trying to locate the softer beep which apparently is unrelated. The louder beep was a standalone battery CO detector that was up in the rafters of the ceiling. I could luckily reach it from an open wall on the other side. No idea why it was there but from previous owners.

  • 1
    An inspection camera might be handy. They usually only need a small hole to look around, instead of the big hole needed for a head.
    – crip659
    Jan 4 at 17:40
  • You would have to look at your system to answer most of these questions "overall battery backup" - "something not wired correctly". We're not there and you haven't given us any details at all about the system itself. Feel free to edit more info into your question.
    – FreeMan
    Jan 4 at 17:52
  • @FreeMan I actually have no idea if something like this even exists which is why I am asking - not specifically about my system. I've checked everything I could visually and all I can see is that there are 10 detectors and a switch on the electrical panel where wiring goes into the ceiling and that's it. I have used search but can't find any mention of an overall battery backup but that doesn't mean it exists. I am asking if there are systems out there where backup batteries for the whole wired system exist, or failsafes for bad wiring with alarms.
    – Vaslo
    Jan 4 at 18:05
  • @crip659 I might have to do this. Do you have one you can suggest or should I ask a professional to handle?
    – Vaslo
    Jan 4 at 18:12
  • 1
    Quite a few connect to your phone and seem inexpensive enough(cheaper than a call fee for someone to come by).
    – crip659
    Jan 4 at 18:26

1 Answer 1


Walking around a house trying to figure out where a faint beep is coming from can be frustrating. If you have done this, and you have successfully determined that it's coming from behind a drywall ceiling in the basement, and you are sure of that .... well: Congrats. You've done the hard part.

You don't need to understand hypothetically how all wired systems work. You need to cut open the ceiling where the beep is coming from. It's possible there is an older detector in there that was left behind when the ceiling was installed. Start by cutting a small hole behind where your dismounted detector went, that way if you are lucky and find the problem there, you can patch it and put the detector back without painting it. If that doesn't help, just know that ceilings are relatively easy to patch because white ceiling paint is cheap and very often you can paint the patch and it matches well. I think that's easier than the path you're taking.

And yes: there are systems with a central battery backup. But when that battery is low, the individual sensors do not beep. Those systems usually have a console or keypad that will do all the beeping and warning for whatever is wrong, including a low or missing central battery. They don't have beepers hidden in secret locations!

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.