The Kidde P3010K-CO is a 10-year, sealed battery, smoke and carbon monoxide alarm 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 alarm’s overall performance and significantly reduces the potential for a nuisance alarm. 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. Industry experts (such as the NFPA), recommend that both ionization and photoelectric smoke alarms be installed to help insure maximum detection of the various types of fires that can occur within the home. Ionization sensing alarms may detect invisible fire particles (associated with fast flaming fires) sooner than photoelectric alarms. Photoelectric sensing alarms may detect visible fire particles (associated with slow smoldering fires) sooner than ionization alarms. Kidde Worry-Free Kitchen Smoke & Carbon Monoxide Alarm Part Number(Ordering Number):21009667. Put smoke alarms at both ends of a bedroom hallway or large room if the hallway or room is more than 30 feet long.