USI Plug-In Carbon Monoxide Alarms offer extreme flexibility as they can easily be inserted into an outlet (no additional wiring necessary). 120v plug-in carbon monoxide alarms are also capable of sensing natural gas (methane). Both versions of the USI Plug-In CO Detector include a 9v battery for continued coverage in the event of a power outage. The use of microprocessor intelligence eliminates nuisance alarms, ensuring that you are warned of actual threats as opposed to annoying chirping. Both plug-in co alarms also come equipped with a silence/test button and an end or service warning that will alert you when it’s time to replace the co alarm (approximately 7 years after activation). Protect yourself and your loved ones from the many dangers associated with carbon monoxide and natural gas (methane) with easy to install plug-in carbon monoxide alarms.