Why Does My Smoke Alarm Only Malfunction in the Middle of the Night?

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I was awakened in the middle of the night to the SHRIEK of the smoke detectors in my house.  Jolted awake.  No sign of smoke or fire.  Headed downstairs quickly--no sign of anything there.  All detectors screaming downstairs.  And finally, down to my neighbors house below.  No noise, no signs of smoke or fire.  Just quiet.

I managed to shut the system by turning off all of the circuit breakers until I hit the correct combination that shut off all five alarms.  Relief.

My dog looked nervous and wanted to leave.  I headed back to bed, starting to nod off when it happened again.  Checked on my neighbor's house--all appeared ok.  I shut off all of the circuit breakers again and once again, headed back to bed.  At this point, the dog was ready to standing near the door, looking bewildered, ready to leave.

And, of course, it happened again.  A quick Google search had me reading articles about electric smoke detectors.  Our building was constructed 10 years ago, and we are the first owners of the house.  Unfortunately, we did not get many manuals with our new homes.  I learned about 5 years ago that each smoke detector has a back up battery that will operate the system if the electricity has failed.  I now change those batteries periodically (not twice a year like I should, but on occasion).  What I learned last night at around 4 AM is that hardwired smoke alarms have a life of approximately 10 years before they fail.  The author of one post suggested that these hard-wired smoke alarms be replaced every 10 years. OK!

I saw several articles, all with titles to the effect of "Why does my smoke alarm keep going off when there's no smoke" or "Why the **** does my smoke alarm keep going off?"  The funny thing, many of these people were writing that their alarms kept going off--but only in the middle of the night. 

I was at the electric supply store early this morning, and returned home with 5 new smoke detectors.  I have replaced two of them so far.  I'm waiting to borrow a tall ladder to get the last 3 changed.

So for those of you out there with hard-wired smoke alarms.  Just remember: an ounce of protection may give you a really good night's sleep.  Change them, it's empowering.  Unless you want to be up in the middle of the night wondering why your smoke alarms only mal function between 3 and 4:30 AM.