why does cold weather set off my smoke detectors?

[Homerboy]

I have 2 wired smoke detectors on my 2nd floor with a crawl space above (gotta be sub zero up there).
This happens once or so every year when the temps get really cold (-10F) right now. - the alarms will go off *usually at like 3am of course giving me a heart attack) It's clearly due to the temps, but I don't understand why it actually happens.

 

[bbhaag]

Electronics to weird things when they go outside of their recommended operating temperatures. Not sure what brand you have but perhaps they are getting to cold and it's causing them to malfunction.
I'm sure the manufacturer has a recommended operational temperature range for them have you tried looking it up?

 

[mindless1]

Diode and transistor values (including those in ICs) can drift with temperature, but it could be something as simple as condensation fouling the sensor. Are your humidity levels on the high side? Could be that with cold weather, furnace running more often, your humidifier is doing its job more often too, in conjunction with a sensor for it that is not quite accurate after some aging.

Do you have adequate insulation above them? If it doesn't have a vapor barrier so heat rises, maybe put a box over that area so no air exchange where the wiring hole is? Or to start with just stuff something in to plug that hole behind the detector if it's open?

Besides increasing insulation, if they are aging, could be a small amount of dust accumulation in addition to condensation so try blowing them out, or of course replacing them.

 

[jmagg]

I've had cobwebs inside smoke detectors cause false alarms.

 

[Greenman]

Smoke detectors also wear out. I don't recall what it is that goes punk, but they do have a fixed life expectancy.

 

[herm0016]

our americium 241 sources have to be sent in to be recombined about every 10 years to keep the activity at about the right level for our uses, always thought that's why smoke detectors had about a 10 year life.

smoke blocks the alpha particles and lowers the activity seen by the sensor, so old ones would go off more easily. less alpha particles per second are being put out by the older source. If there was some drift to the values of the electronics. 10 years is not too much for something with a half life of 432 years though.

why not unscrew them and make sure there is not a hole above them letting cold air in to them, and if there is, spray foam it, if not, replace. they are not expensive.

 

[Fanatical Meat]

Smoke detectors also wear out. I don't recall what it is that goes punk, but they do have a fixed life expectancy.

This and many of the new ones sold don’t have changeable batteries, plus they beep like mad when they get to the end of their life.
Pain in the ass but a smart design. No more taking the battery out to stop the noise, no more I’ll ignore it and replace “some day”
New doctors are designed to hound you to replace them.
You really should replace them every 7 years.

 

[Homerboy]

This and many of the new ones sold don’t have changeable batteries, plus they beep like mad when they get to the end of their life.
Pain in the ass but a smart design. No more taking the battery out to stop the noise, no more I’ll ignore it and replace “some day”
New doctors are designed to hound you to replace them.
You really should replace them every 7 years.

These are wired, with battery backups and replaced just 2 years ago.
I'm going with the warm/cold condensation theory

 

[Greenman]

These are wired, with battery backups and replaced just 2 years ago.
I'm going with the warm/cold condensation theory

That would indicate an insulation issue in the attic. Would be worth having a look.

 

[Homerboy]

That would indicate an insulation issue in the attic. Would be worth having a look.

Well, one is on a vaulted ceiling so not much room between the drywall and the shingles. It is fully insulated though and is only ~10 year old construction. That's probably the main problem when it's hitting -10 or lower at night.

 

[herm0016]

at least take them down and seal the holes in the electrical box or get some of the foam gaskets for electrical boxes. this will help quite a bit.

 

[Homerboy]

at least take them down and seal the holes in the electrical box or get some of the foam gaskets for electrical boxes. this will help quite a bit.

Well I took them down for right now as this arctic blast is supposed to be around all week and I don't need the heart attack at 3am every night. I just hope there's no fires in the house this week
That's a good idea of sealing them off.

 

[Fanatical Meat]

Maybe you want a heat detector vs a smoke detector.
I get the the combo smoke detectors are typically better for home use but if it is sending so many false alarms it sort of defeats the purpose of having it.
I think a guy I kind of know had a similar problem with his RV if I see him I’ll ask what the solution was.

 

[Homerboy]

Maybe you want a heat detector vs a smoke detector.
I get the the combo smoke detectors are typically better for home use but if it is sending so many false alarms it sort of defeats the purpose of having it.
I think a guy I kind of know had a similar problem with his RV if I see him I’ll ask what the solution was.

It's not "so many" false alarms. It's literally maybe once a year during these super-cold snaps. I was just more curious as to what was causing it versus it being an actual "problem"

 

[Leymenaide]

Could be low humidity and more fine dust particles. Take unit down and blow it out with compressed air. If that does not work think about replacement. After five years I buy 2 replacements at a time, I find I use them.

 

[Mr.IncrediblyBored]

Are they combo smoke-CO detectors? If you have a small exhaust leak, could also be elevated CO levels with your furnace running round-the-clock during those cold snaps. Might be a good idea to buy a CO monitor if you don't have one.

 

[MtnMan]

What are the min/max operating temps for what ever model is mounted in the non-conditioned space? Most list the operating range between 40 to 100 F.