This compact 30-hour Ultrasonic Cool Mist Humidifier guards against problems caused by dry air in the home. It features an easy to fill. 50 Gal. tank, ideal to use on table tops, for use in small to medium rooms. Unlike other humidifiers that grow slimy mold on the water tank surface, Silver Clean Protection is embedded in the tank to help keep the tank cleaner longer. 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. It has an optional aromatherapy tray so a few drops of essential oil can be added to create a relaxing atmosphere. A low water indicator light lets you know when it's time to refill the water tank and auto shut off feature when the water is too low. 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 setting and cool mist, also depends on atmospheric conditions.