This Pure Guardian Top Rated Ultrasonic Cool Mist Humidifier enhances comfort, helping you sleep better. It provides quick relief from dry air making life pleasant for those with colds, allergies and dry skin. It features an easy to fill .5 gallon tank, ideal for use in small sized rooms. It delivers up to 4L of moisture output per day. Unlike other humidifiers that grow slimy mold on the water tank surface, Silver Clean Protection is embedded in the tank to fight the growth of mold and mildew on the surface of the water tank.