Works during power outages. No installation required. Place or mount almost anywhere. Mute button to quiet unnecessary alarms, also tests alarm function with same button Loud 85-decibel alarm, low battery warning. Low battery mute quiets low battery signal for up to 8 hours. Easy access front-open compartment allows battery change without taking alarm down. Electrochemical sensor is the most accurate technology available for detecting carbon monoxide. End of life timer alarm chirps when it is time to replace the alarm. Meets UL2034 standard. 5 year limited warranty. Uses 2 AA batteries, included.