Dry air lowers the defenses of the throat and nose, making us less resistant to bacteria and viruses such as influenza, thereby increasing our health risk. Although there is a growing need for humidifiers, many conventional products are intended for home use only, so it is difficult to satisfy the demand for use in other settings. To resolve this issue, we have developed a portable humidifier. By using a plastic bottle or something similar, like a water tank, and adopting USB power, we made it possible to humidify variety of spaces, including homes, offices, hotel rooms, and vehicles.