The Lifesmart Ultimate Digital Ultrasonic Cool Mist Humidifier guards against problems caused by dry air in the home. This especially occurs during the winter when homes are heated and the windows are closed. Ultrasonic technology disperses a fine mist into the air and is ultra-quiet making it ideal to have on while you sleep. The extra large tank can provide soothing mist for up to 34 hours on low. There are 3 speeds low, medium and high. Digital controls allow you to set the desired humidity from 45% to 85% in 5% increments. Once the desired humidity is reached the unit will shut off to save water and extend runtime. Also included is a digital timer. Safety features include an auto shut off do prevent damage. Enjoy healthy air today with the Lifesmart Ultimate 1 Gallon Ultrasonic Humidifier with Digital Humidistat Control.