The Kidde Firex Hardwired Smoke and Carbon Monoxide Detector with Battery Backup and Voice Alerts, model 900-CUAR-V, is a hardwired smoke alarm and carbon monoxide detector combo. It connects to your home's wiring (120-Volt AC power), while 2 AA batteries (included) provide battery backup during the event of a power failure. If the smoke and carbon monoxide alarm detects smoke, fire, or carbon monoxide, an 85-decible alarm and voice alert will sound stating, Fire. or Warning: Carbon Monoxide The combination smoke and carbon monoxide detector also provides a voice alert of Low Battery when the battery on the unit needs to be replaced. The Kidde Smoke and Carbon Monoxide alarm uses photoelectric sensors that detects visible fire particles associated with slow smoldering fires, as well as an electrochemical carbon monoxide sensor, which offers readings of carbon monoxide. When the backup battery is nearing the end of its life, the alarm will begin to chirp. In the case of nuisance or false alarms, the Hush feature temporarily silences this detector. Install a smoke detector and carbon monoxide detector on each level of your home, in hallways and inside each bedroom. The smoke detector and CO alarm is capable of hardwired interconnection to other select Kidde alarms for whole-home activation - when 1 alarm sounds, they all do. UL Certified with a 10-year limited warranty. Meets requirements of UL 2034, UL217, NFPA72, The State of California Fire Marshal, NFPA 101, FHA, and HUD.