Nighthawk, AC Powered, Plug In Carbon Monoxide Alarm With Battery Back Up & Digital Display, Easy To Install, Provides Reliable Protection Against The Dangers Of Carbon Monoxide, Digital Displyay Feature Adds An Advanced Level of Protection Showing CO Levels In PPM Allowing You To See If Levels Change, Written Information & Instruction, Operation Easy To Understand, Small Sleek Design, Suitable For All Living Areas, 7 Year Limited Warranty.