Why do our smoke detectors go off at 3 am?

Old 10-12-05, 12:08 PM
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Why do our smoke detectors go off at 3 am?

I live in a community where several houses are having issues with their smoke detectors/alarms going off at 2, 3 or 4 a.m. We've heard and rounded up all the usual suspects: spiders, spider webs, dust, lint by the smoke detectors, faulty wiring, bad fuse in circuit breaker, ceiling fans generating too much heat, bad batteries, low batteries, dead batteries, bad detectors. You name it, we've heard it. We've replaced, in several houses, ALL of the units. I should indicate all the detectors are wired together, so when one goes off, they all go off (sometimes they are tied into an independent "alarm system", sometimes not). They will go off - push the test button - for that amount of time. But then they will do it 10, 15, 20 minutes later. Sometimes for several nights in a row, sometimes 1 night, but then again in 4 - 6 weeks or 4 to 8 months. It seems it is always in the 2 - 4 am time frame. We have swept, vacuumed the units, replaced all batteries, replaced one or all units. Someone indicated perhaps the power company is doing an automatic reading of the meters and it is sending some "signal" or frequency that is being interpreted by the detectors as something bad.

Sorry this is so long, but any ideas? Could it be an outside factor like the electric company doing something? Seriously, it is almost always 2 or 3 or 4 in the morning. Why that time?

Thank you,

Old 10-12-05, 05:04 PM
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Humidity. Most likely, at those hours, the moisture in the air is condensing in the detectors, just enough to fool them into alarming. If they are all of a similar age and model, and it's a mass-built community, there could have been a bad batch from the manufacturer, but it sounds like a varied swath.

If you are having foggy mornings when these incidents happen, that would be my best guess.

The electric fluctuation issue has some possibilities, but if this is happening with alarm system smokes (which work on filtered 12vdc from the alarm system), then the most likely culprit is environmental.

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