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 small to medium rooms. Silver Clean™ Protection is embedded in the tank to help keep the water 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. It also features a soft glow night light. 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.