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 CO 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.