Holmes 1.5-Gallon Ultrasonic Humidifier for medium-size rooms increases the benefits of good air quality and provides relief from some of the harmful effects associated with dry air. The unit also produces a cool mist that can be seen and felt, plus it offers variable mist control for your optimal comfort. It also features a rotating nozzle as well as an empty tank indicator. Runs up to 24 hours per tank filling; Variable speed settings for optimal comfort; Empty Tank Indicator; Rotating nozzle for directional mist; Shatterproof tank; Contains an Antimicrobial Additve and Arm & Hammer treatment in key plastic parts.