Combo Smoke and Co Detecor: Features electrochemical Carbon Monoxide sensing technology and photoelectric smoke sensor optimized to detect larger smoke particles produced by smoldering fires; helps minimize the number of false alarms 10 Year Battery Operated: This combination smoke detector and carbon monoxide detector alarm provides 10 years of continuous power with a built-in lithium battery; provides continuous monitoring of smoke and CO levels, even if there's a power failure; an end-of-life signal will let you know when its time to replace the unit for safety Test/Slience Button: Tests the unit for proper operation and resets the carbon monoxide alarm,Alarm Practical LCD Display: Clearly indicates real-time carbon monoxide (CO) concentration in the surrounding air, as well as the remaining battery life and working status of the alarm; if a CO concentration of 30-999 ppm exists for a certain time period, the screen will be backlit blue, and the LED indicator will flash red 4 times every 5.8 seconds A loud 85-decibel alarm sounds when Carbon Monoxide, and Smoke levels begin to rise,Easy to Install and Use: The alarm can easily install with mounting bracket.No hardwired anymore