The First Alert Combination Explosive Gas and Carbon Monoxide Alarm features a backlit digital display and detects propane, CO, and methane gas. This explosive gas and CO detector plugs into any AC outlet with no additional mounting hardware needed. Designed to promote peace of mind and household safety, the Combination Explosive Gas and Carbon Monoxide Alarm senses the presence of methane and propane. It also features an electrochemical CO sensor that detects carbon monoxide. When the alarm detects a threat, it alerts you with a loud 85-decibel alarm