The 70-hour ultrasonic cool mist humidifier guards against problems caused by dry air in the home. It features an easy to fill 3.79 L (1 gal.) tank, ideal for use in medium sized rooms. The 2-pack allows you to have units in multiple 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.