DescriptionSize Name:1 Pack The Kidde P3010K-CO is a 10-year, sealed battery, smoke alarm and carbon monoxide alarm the features photoelectric and electrochemical sensing technology and Smart Hush feature. This combination alarm combines the detection capabilities of a photoelectric sensor with that of an electrochemical sensor, which is used to detect CO. When either sensor notices a potential hazard, it will communicate with the other. Depending on what is detected, the alarm will adjust its smoke sensitivity in order to better discriminate between a real hazard and a false one. This constant communication enhances the alarm's overall performance and significantly reduces the potential for a nuisance alarm. At the end of the alarm life, the unit will chirp, indicating the alarm is in need of replacement. The sealed-in lithium battery will power the unit for the entirety of its 10 year life, eliminating the need for battery replacement and ends worry of unauthorized battery removal. Provides continuous protection, even during power outages.