Combination carbon monoxide & smoke alarm. Detects smoldering and fast-flaming fires as well as carbon monoxide. Dramatically reduces the chance of nuisance alarms. Features Intelligent sensor technology which combines the detection capabilities of an ionization smoke sensor with an electrochemical carbon monoxide sensor. Capable of interconnecting with up to 24 Kidde devices. (2) AA battery back-up in case of power outage, batteries included. Battery life varies according to use and application. Features a front-loading battery door for easy battery replacement. Battery door will not close unless the batteries are properly installed. Adjustable mounting bracket makes installation fast and easy. Also works with existing smoke and combination smoke/carbon monoxide mounting brackets. Hush setting temporarily silences nuisance alarms for approximately 9 minutes. Red & green LED (light emitting diode) indicators for added safety.