I accept that it is probably ghosts.

June 9, 2017 6:04 AM

The smoke detector at the top of our stairs chirps once or twice every morning sometime between 7 AM and 9 AM. It's not any of the usual things.

I've replaced it with a new one twice now, using a new battery each time - so, it's not the battery, and it's not the expiration warning. It's unwired, so it's not some kind of line voltage issue. It's brand new (and the behavior has survived replacement), so it's probably not bugs. (And in general we've almost never seen a bug in our house.) It's always in that time window (and I've been home sometimes all day for days). The time window spans seasons, so it's not light falling on it from a window at a particular time. What is going on!?

posted by dmd to Home & Garden (16 answers total)

My first guess would be that the temperature in your house had reached dewpoint; that just sufficient condensation was occurring so that moisture was gathering on the sensor enough to trigger a reading.

But I am also doubtful of that theory because it seems to me that the days of smoke detectors going off every time you take a shower are over, and they no longer shrill false positives from moisture.

Alternatively, if your house is at its coolest point at 7 or 9 AM it may be failing then because of a dud battery on its last legs. A cooler temperature slows down the chemical reaction necessary for a battery to work. - but you said you changed the battery. So have you tried changing brands? If you got all the batteries from the same Costco bulk pack of 80 batteries they may all be slightly weak. You could try shopping at a different location and getting a completely different brand of battery.

(Please do not buy Energizer batteries. Energizer = Union Carbide. Union Carbide is the company that caused the Bhopal disaster (3,787 to 16,000 dead) and spent years fighting to avoid being held responsible.)
posted by Jane the Brown at 6:43 AM on June 9, 2017 [2 favorites]

Have you unbatteried it for a period of several hours and then rebatteried it to see whether it's actually "between 7 and 9 a.m." or more like "every 24 hours from an unknown start point"?
posted by Etrigan at 6:57 AM on June 9, 2017 [5 favorites]

If you move it to a different location for a few days, does it stop doing this?
posted by Lafe at 7:08 AM on June 9, 2017 [1 favorite]

Could it possibly be a daily check tone? A signal that it is functioning correctly? Or maybe needs service?

This page says intermittent chips can be a signal the alarm needs service, is obstructed, or has reached the end of its life.

You can find a lot of owner's manuals online now, if you can find the brand and model number you can probably find the manual.
posted by Cranialtorque at 7:50 AM on June 9, 2017 [2 favorites]

As per Jane the Brown's reply, I was thrown by a batch of duff batteries at one point. I bought a different brand, and now several older smoke alarms which I'd replaced are fully functional again.
posted by rd45 at 7:54 AM on June 9, 2017 [3 favorites]

@rd45 samesies. I've put in "new" batteries into smoke alarms only to have them chirp at night (it gets cold I suppose?). Once I got a new pack of batteries, those worked fine.
posted by pyro979 at 7:59 AM on June 9, 2017

I've certainly dealt with replacing bad batteries with...bad batteries. A voltmeter is your friend in this case.

But I think it's probably ghosts.
posted by TinWhistle at 8:05 AM on June 9, 2017

> But I am also doubtful of that theory because it seems to me that the days of smoke detectors going off every time you take a shower are over, and they no longer shrill false positives from moisture.

LOLOLOLOL. [cries] No, it's still a thing.
posted by desuetude at 8:58 AM on June 9, 2017 [5 favorites]

Do you still have the steam radiator system you asked about in a previous question?

If so, I nominate gas vented from a radiator when the morning load hits your system.

Such gas is much more likely to trigger a smoke detector than shower steam because of corrosion and clogging inhibiting additives with a significant vapor pressure which are almost universally present in boiler water these days.
posted by jamjam at 10:24 AM on June 9, 2017

Are you sure it's not a different alarm? The way the sound travels with that chirp can be deceiving.
posted by bongo_x at 10:34 AM on June 9, 2017

Response by poster: The batteries all have checked out with a voltmeter. It still happens in summer, and there's no radiator near there anyway. The "is it really then or every 24 hours" is interesting - I will try altering the startup time and see!

It's definitely that alarm.
posted by dmd at 10:36 AM on June 9, 2017

Is this a photoelectric smoke detector or an ionizing one or a combination of the two or one that adds CO detection to the mix?

It's not going to help *me* answer the question, but the answer might inspire someone else.
posted by It's Never Lurgi at 10:43 AM on June 9, 2017

Response by poster: Photoelectric, no CO.
posted by dmd at 12:22 PM on June 9, 2017

Are you certain the chirps are coming from that specific smoke detector? Is it possible it is coming from a different one in the house - or even one that you don't know about from a previous owner that is nearby?
posted by Toddles at 9:44 PM on June 9, 2017

If it's photoelectric, have you tried cleaning that part of it? We had mysteriously chirping detectors and it turns out the "eye" was dusty, due to a small home improvement project. A little vacuuming (or compressed air) stopped the chirping.
posted by sarajane at 5:34 AM on June 10, 2017

Seconding Toddles' question. We thought one of our detectors was malfunctioning but it turned out to be a dying battery in an old detector that was left in a box by a previous electrician!
posted by purple_bird at 2:19 PM on June 12, 2017