Got a call today that The Smoke Detectors were activating during the night.There is 4 of them and it seems that this has just started with the cold Temperatures .They are 8 years old, all i could was suggest was to have them replaced.
They're supposed to be replaced after 10 years anyway, so this is a good opportunity. The last ones I had go off was with a cleaning lady using a vacuum. It was throwing off dust because the bag was full.
What you could have is a problem with codensation. If it's conduit, your (his) warm moist house air travelling through the cold attic will cause water to form in the pipe and drip down. If it's romex, I don't know, but I wouldn't rule out condesation.
I have seen this many times where the water shorts out the smoke. That's why I never run conduit straight up out of a wall or ceiling box and extend it into open attic. Always follow the contour of the insulation for as long as you can. If you have to up to an attic light, put a few 90's before you fly. This way any condensation will have a chance to re-evaporate as it warms back up.
I use to tell the H.O to vaccum the smokes once a month, specially if they had a hot air system. Also, for a little more investment, install the photo instead of the ionization type. Photo is less nuisance alarm and I always worried that they would unplug the ION types and forget they were unplugged.