Protect your family from the dangers of carbon monoxide (CO) exposure with the Kidde KN-COPP-3 Nighthawk Plug-In Carbon Monoxide Alarm with Battery Backup and Digital Display. The Nighthawk is an easy-to-install unit that provides reliable protection against the dangers of CO. It features a digital display that shows CO levels in parts per million allowing you to see if, how, and when levels change.