The Nighthawk model KN COP DP LS AC Powered, Plug In carbon monoxide alarm with battery backup and digital display is an easy to install unit that provides reliable protection against the dangers of carbon monoxide. Digital display feature adds an advanced level of protection showing CO levels in PPM allowing you to see if levels change. Written information and instruction make this units operation easy for anyone to understand. The Nighthawk AC/DC Digital alarm has a small, sleek design that is suitable for all living areas and has a 7 year limited warranty.