Keep your home safe by continuously monitoring for dangerous CO levels with the Kidde Battery-Operated Carbon Monoxide Alarm with Digital Display KN-COPP-B-LPM. It has been carefully designed and tested to detect CO concentration levels as low as 11 and up to 999 PPM (parts per million). This Kidde Carbon Monoxide alarm features a digital memory display that allows for easy viewing and storing of the levels in your home. It also includes a slide-out battery door that gives immediate access to the batteries and a safety feature that makes it difficult to close the cover without them being installed. The test/reset button lets you test the unit?s electronic horn or reset it during an alarm. This battery-operated carbon dioxide alarm will continue to detect even during power outages. It is suitable for all living areas.