I had a new home built in 2012 that came with five of these USI Electric / Universal Security Instruments, Inc. MICN109 smoke, fire, carbon monoxide, and natural gas alarms. They would randomly start beeping on a low battery alarm despite having brand new batteries installed. They gave false CO and natural gas alarms. I went through THREE sets of these - all replaced under warranty. Finally, I had enough of the false alarms in the middle of the night, so I ripped every last one of them from the ceiling and replaced them with Nest Protect smoke and CO alarms.