Silent, no fan, whisper quiet works continuously without knowing if for 15+ years. * Compact Design, less than 4″w x 6″h x 2″ deep, weighs less than a pound. * No Filter, self contained, no parts or chemicals to replace or change. * 4 Watts, runs 24/7 wih less than 4watts/hr-less than most night lights. * Just Plug In, for years of silent uninterrupted springtime fresh air.