ETvalley USB Cool Mist Ultrasonic Humidifier Silent for Baby Room, Living Room, Cars and Office ETvalley designed the humidifier to be the most silent possible, perfect for baby room, living room car and office. The humidifier will produce ultra-thin mist thanks to its high frequency ultrasonic technology and it will quickly purify the air around you. Really easy to use, you just have to put the humidifier into a water source. Power it with the micro USB cable and you are ready. Humidifier is created to last up to 12 hours when it is used with a big water source and will last up to 5 hours in the water cup. You will be able to take humidifier with you anywhere you want, it can work with a power bank, so the air around you will always be pure.