Hunter 31004 bacterial shield ultrasonic humidifier solves the problem of dry air in your home. Ultrasonic technology uses sound vibrations at a very high frequency to produce the humidity. Micro ban antimicrobial protection only on hunter humidifiers helps prevent odor-causing bacteria mold and mildew on the humidifier. Wick free - no wick to replace ever - means more cost savings and less maintenance for you. Intended for use in small rooms it has an 18-hour run time. Included demineralization tablets remove minerals from the water to prevent "white dust". 3-year limited warranty.