The Kidde P3010CU is a 10-year, sealed battery, smoke and carbon monoxide alarm with a voice warning system that features photoelectric and electrochemical sensing technology with 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 alarms overall performance and significantly reduces the potential for a nuisance alarm. The voice warning system announces Fire , or Warning, Carbon Monoxide to help eliminate any confusion and clearly warn you and your family of a smoke or carbon monoxide danger. The sealed in lithium battery will power the unit for the entirety of its 10 year life, eliminating the need for battery replacement and worry about unauthorized battery removal. The alarm provides continuous protection from smoke and carbon monoxide, even during power outages. The alarm will automatically activate when it is attached to the mounting bracket; there are no pull-tabs, no switches, everything is automatic. At the end of alarm life, the unit will chirp, indicating the alarm is in need of replacement. The customer can use a simple tool such as a screwdriver to deactivate the unit, stopping the chirp and making it safe for disposal.