The leading cause of accidental poisoning deaths in North America, Carbon Monoxide (CO) is odorless, tasteless and invisible - it"s a silent killer. The only safe way to know if carbon monoxide is present is to install carbon monoxide detectors (alarms) on every level of your home and in sleeping areas. Kidde has been making CO alarms with electrochemical sensing technology for years. All of Kidde"s CO alarm products - from basic units to premium CO alarms - include the company"s patented Nighthawk electrochemical CO sensor. Features Written Information & Instruction Operation Easy To Understand 7-Year Limited Warranty