Protect homes and businesses when using the First Alert CO400 Battery Operated Carbon Monoxide Alarm. This sensor is designed to last for up to five years and does not require installation. The alarm can be mounted or placed nearly anywhere and in any room. The First Alert carbon monoxide alarm is powered by batteries so this device is portable. This product features a loud 85-decibel alarm that triggers when carbon monoxide levels become elevated. It also features a silence button and test button so it can give peace of mind.