Ionization sensor smoke detector. Features wide openings for smoke entry. Uses a 9V (volt) battery designed to last up to 1 year. Battery life varies according to use and application. Repeated beeping warns when battery needs replacing. Loud 85 decibel alarm horn and test button. Compact design measures 4-3/4 inches x 6 inches. 3-year limited warranty. UL (Underwriter’s Laboratories) listed. 9V battery included.