We purchased a 17-year-old home in Florida (USA) a few months ago, that has seven smoke detectors (one in each of its four bedrooms, two in hallways, and one in the main living space).

A few days ago, the smoke detector in the main living space began going off in its alarm state in the middle of the night. After verifying it was a false alarm, I silenced it and we all went back to bed. The next day I checked all 7 units and found four of them were original to the home, including the one issuing a false alarm. The interconnect wires were all disconnected as well. We decided we would go ahead and replace all 7 and interconnect them.

So far, I have done two replacements: the guest bedroom and the main living space. This morning, the one in the guest room began alarming which triggered the living room alarm as well.

Is the likeliest explanation that we're just unlucky--that we had an aging alarm that went into alarm state because of its age, and a few days later had an insect or something crawl into a different alarm? How can we troubleshoot this? My wife and son have sleep issues, and anxiety that at any time the smoke detectors may begin going off is not helping. Not to mention the damage to sensitivity that repeated nuisance alarms may cause if there is ever a real fire.

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    Are they ionisation or optical types? The failure modes are rather different. Especially if all the failures are in the originals, and they're ionisation units from the same batch, it could well be that they've reached the end of their useful lives in quick succession - a coincidence but not a remarkable one – Chris H Apr 29 '20 at 10:45
  • To add to Chris’s comment, it is high pollen in my area and sometimes that sets them off when my wife is cleaning , a shot of canned air may well set them off when blasted but usually clears dust and pollen that can set them off. – Ed Beal Apr 29 '20 at 13:38
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    First failure was in an original. I believe they were all photoelectric. Second failure was in a brand new one, a Kidde “TruSense” which is a combo/dual sensor model in a bedroom. – samh Apr 29 '20 at 22:00
  • After the first false alarm with the new smoke alarms everything has been fine. Until tonight we were all awoken in a panic with another fase alarm (different room). – samh May 30 '20 at 6:26
  • I have had a very similar situation. After a few nuisance alarms, I replaced the old detectors with new ones. The new ones also periodically alarm also. I have two that are dual detectors and the rest are ionization only. Various ones will alarm without explanation and at least once, twice in one night by different alarms. Usually, though, it's 3-4 months apart, making it hard to debug. I suspect it could be related to the power source, but I'm not sure how to test that theory. – Jonathan Swinney Jun 28 '20 at 19:50

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