I have a smoke alarm that keeps beeping every 30 minutes or so even after I replaced the battery. I'm thinking it's probably time to replace it.

I'm trying to figure out if it's hardwired or battery powered. How do i tell?

There is a 9v battery that needs to be replaced, but I think both hardwired and battery smoke alarms both have 9v battery for backup power.

  • IIRC, that might actually be a warning beep that the sensor can no longer auto-calibrate, and the unit could be faulty. The every 36-ish seconds means low batt. Even if it's fully operational, you probably want to get rid of the chirp anyway.
    – dandavis
    Oct 25 '18 at 16:24

If it is hardwired then there will be a cable going to each smoke detector. It is usually pretty obvious. If you don't see anything then see if you can remove the smoke detector from the ceiling. If you can remove it easily (typically by twisting it slightly and then pulling away from screws and/or a mounting bracket) and it comes off (except possibly for a small mounting bracket) then it is battery powered. If you try to remove it and find it is hanging by a cable the it is hardwired.

If all that doesn't make sense, post a picture of it and we'll see what we can figure out.

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