The 70-hour Ultrasonic Cool Mist Humidifier guards against problems caused by dry air in the home. It features an easy to fill 1 gallon tank, ideal for use in medium sized rooms. 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. Thanks to ultrasonic technology, it disperses a fine mist into the air, and is ultra-quiet making it ideal to have on while you sleep. The humidifier emits a soothing cool mist, and a low water indicator light lets you know when it’s time to refill the water tank. Night light feature makes it a great addition to kids’ rooms. PureGuardian humidifiers create a better home environment for those suffering from colds, allergies and dry skin. Note: Run time is based off of running the unit on low speed, also depends on atmospheric conditions.