The Kidde 900-0121 is an AC wire-in carbon monoxide alarm that protects you and your family from the dangers of carbon monoxide. The digital display allows for continuing monitoring of carbon monoxide levels. Its multiple contractor friendly features ensure easy installation and minimal troubleshooting. This alarm interconnects with up to 24 Kidde devices including smoke alarms, carbon monoxide alarms and heat alarms on one wiring network. The 900-0121 includes a 9 VDC battery back up for continuous protection in case of power failure. It has a 7 years life a 5 years limited warranty.