False alarms in hard-wired smoke alarms?

August 24, 2007 9:56 AM

What causes false Alarms in hardwired smoke detectors?

Last night around 2am, all three of the hard-wired (not battery powered) smoke detectors in our apartment went off. We were unable to use the reset buttons and had to physically disconnect them to get the alarm to go off.

There was no smoke or other sign of a real threat that could have set them off. I suppose it could have been low levels of carbon monoxide and that will be the first thing we'll try to rule out tonight.

Any other ideas as to what could have caused this and what we should do? I've had smoke alarms go off when they run out of batteries before, but never anything like this.

posted by morallybass to Home & Garden (14 answers total)

This happened to us a few times in the last few months also. It's scary and also very annoying. I haven't been able to find any cause of it. Our detectors are not CO detectors, so it's not that (in our case) (we have seperate CO detectors)

I've wondered if it's like a power surge or something. Sorry I can't answer your question, but at least you know it's not just you.
posted by RustyBrooks at 10:05 AM on August 24, 2007

We've had our fairly new wired smoke detectors go off. Ours are photoelectric detectors. The first time this happened I called the fire department. They said to check for a bug in the detector itself. Since then I've had a spider web set it off. I've also had a "bad detector" wreak havoc, since when one sounds off they all do.

By the way, unless they're labeled as such, normal smoke detectors will not detect carbon monoxide.
posted by SteveInMaine at 10:14 AM on August 24, 2007

Dust can cause this too. Perhaps a shot of compressed air will help.
posted by caddis at 10:24 AM on August 24, 2007

This happened in my house several weeks ago. I live in a condo building where all of the smoke detectors are networked as such, and needed to call the fire department because I didnt have access to the other apartments.

In the end, it turned out that some dust had gotten into the detector in the attic of one of the units.
posted by jozxyqk at 10:29 AM on August 24, 2007

Response by poster: Thanks for all the help guys.

We have three of them, and they seem to be all wired together as you've described. We were unable to get all of them to stop sounding until we disconnected the one on the top floor, I guess that one must have been responsible.

Since we're renting, the only thing I know about the detectors is what I read on the back of them in the middle of the night. It does seem that it was the CO alarm that was going off.
posted by morallybass at 10:30 AM on August 24, 2007

.. oh, and the firemen told me that the one causing the problem would have a red light, while the rest would have a green light. It may differ with your model, but there should be a way to figure out which one is complaining.
posted by jozxyqk at 10:32 AM on August 24, 2007

if it was carbon monoxide, i'd be concerned - you say "low levels" but afaik it's colourless and odourless so it seems you're just guessing, no? the co alarms seem to be a lot less sensitive/susceptible to false alarms than smoke alarms - we have one in the kitchen - which just failed an official examination for adequate ventilation - and it has never sounded.
posted by andrew cooke at 11:20 AM on August 24, 2007

If this is a CO only detector I would be concerned. Those don't really have false alarms to my knowledge. The fire department has sensitive monitors which can tell you whether you have CO in your dwelling. If you are not comfortable calling them, the at least get another CO detector as a reference. On the other hand, if it is s combined smoke/CO detector it is likely just dirty.
posted by caddis at 11:27 AM on August 24, 2007

dust and spiders are two common culprits. and if they're all hardwired together (the detectors, not the spiders and dust), then one going off will trigger the others.

i'd agree with the "spray compressed air" idea.
posted by rmd1023 at 11:41 AM on August 24, 2007

As many other mentioned, I also had this same problem as well.
What I didn't know is that many electrical smoke detectors also have batter back-ups. In my case, both of my battery back-ups were going bad. I found somewhere on the company website that this can happen. I ended up replacing both as i could not figure out to replace the battery backups with out distroying the unit.
posted by lutzla23 at 11:56 AM on August 24, 2007

If you live in an especially humid area, and leave your windows open, it's not unheard of for humidity to trigger fire alarms.
posted by almostmanda at 12:07 PM on August 24, 2007

same here...same thing. Must be insanely common. Happened in my latest house a few months ago too.
posted by evilelvis at 12:15 PM on August 24, 2007

Morallybass, reconnect the detectors. If they sound again, and its CO like you just said, call the fire department. If there really is CO present, by the time you feel the effects you could become seriously ill. Call the fire department.
posted by C17H19NO3 at 1:48 PM on August 24, 2007

We blow ours out with Dust-off periodically. If the issue is spiders, you can invert the can of dust-off and freeze the little buggers.
posted by dws at 11:56 AM on August 25, 2007