The 120-hour* Ultrasonic Warm and Cool Mist Humidifier guards against problems caused by dry air in the home. It features an easy to fill large 2 gallon tank, ideal for use in large rooms. Thanks to ultrasonic technology, it disperses a fine warm or cool mist into the air, which can be extended using the wands. It is ultra-quiet making it ideal to have on while you sleep. Smart mist sensor monitors the level of humidity in the room and adjusts to your selected level. The humidifier is equipped with an easy to use digital display, a night light, timer and 3 speed mist control. A low water indicator light lets you know when it's time to refill the water tank. PureGuardian® humidifiers create a better home environment for those suffering from colds, and dry skin. Note: Run time is based off of running the unit on low setting and cool mist, also depends on atmospheric conditions.