The Kidde i5000 is an AC/DC powered, ionization smoke alarm that operates on a 120V power source with 9V alkaline battery back-up. This alarm uses ionization sensing technology. Ionization sensing alarms may detect invisible fire particles (associated with flaming fires) sooner than photoelectric alarms. Photoelectric sensing alarms may detect visible particles (associated with smoldering fires) sooner than ionization alarms.