The Universal Security Instruments Electric MCND401 Plug-In Carbon Monoxide and Natural Gas Smart Alarm is a 2-in-1 device that provides double the protection with a single installation. This dual-sensing alarm protects against two deadly household threats: carbon monoxide and natural gas (or methane). Perfect for new or replacement installations, the 120-volt AC alarm is suitable for houses, apartments and mobile homes. The compact plug-in design covers only (1) outlet for a fast and easy installation with no wiring required.