Electrochemical sensor technology detects CO gas Easy installation, no wiring needed, detects during a power failure by operating on 2-AA batteries (included) Conveniently designed & portable: simple to install on a wall of your home or place on a tabletop Green LED indicates power to the carbon monoxide detector, while an 85-decibel alarm & a red LED indicates the presence of carbon monoxide Event Memory records the last time carbon monoxide was detected or when the unit was last tested Test-Hush button makes it easy to test the carbon monoxide detector or temporarily silence the low battery chirp warning UL Certified, 10-year limited manufacturer warranty