This First Alert detector is a combination Explosive Gas and Carbon Monoxide Alarm. It detects propane, carbon monoxide, and methane gas. It features a built-in backlight digital display and can plug into any AC outlet. The easy-to-read digital display shows the current and peak levels of gas detected. It plugs into any AC outlet and has backup power in case of a power outage. The alarm is quite loud at 85-decibels to ensure it is heard clearly.