Electrochemical carbon monoxide sensor. Covers only one wall outlet. Plug the alarm into a regular outlet, test, and it's ready. Battery back-up keeps alarm working if electricity fails. Point and click any remote control unit to quiet unwanted alarms (remote not included). EZ view backlit digital carbon monoxide level display to view danger levels, current, and peak CO levels. Memory stores, recalls, and displays highest levels of CO detected. Low battery warning, low battery silence quiets low battery alert without affecting alarm operation. End of life timer alarm chirps when it is time toreplace, should be replaced every 5 years for maximum protection. Loud 85-decibel alarm. 3.3" height x 4.75" width x 2.8" depth, 0.54 pounds. UL Listed. 5 year limited warranty. Uses 2 AA batteries, included.