This humidifier has two mist modes: Continuous and intermittent mode. On continuous mode, it will automatically shut-off after 4 hours. On intermittent mode, it will automatically shut-off after 6 hours. It shut-off when the water level is low. Thus, you don't have to worry about the humidifier being damaged in the absence of water. You can use it at night without worrying about safety. The portable USB humidifier is very easy to operate. One button controls all functions, you simply need to press the power button every 1 second to control the mist. Keep pushing power button for 3 seconds to enable the night light and colorful light function.