Service call this afternoon coming up. Customer claims he now has eight recently installed Kidde 120 volt interconnected photoelectric smokes with battery backup. These were installed in February by another electrician to replace his existing smokes which would intermittently alarm (every two months or so). Now he has had the same issue (alarmed last night in the middle of the night) with the new ones. I'm thinking either he has some loose connection in the wiring somwhere which drops out power temporarily or there is actually, or possibly a CO detector that is also interconnected and is actually sensing CO or needs cleaning. Or, that there is a unit too close to a supply/return duct, shower area, etc. Any ideas beyond this? He just paid $800 to have the (8) smokes replaced in February.:001_huh: I have not run into this issue before, just the beeping issue.