Normally people can breathe through either the mouth or the nose, and will unconsciously switch the two when they eat, speak and exercise. However, no way do people use the same cavity to breathe through the mouth and the nose. Existing masks are mostly designed into a single respiratory space for both the mouth and the nose. Such design only partly solves the problem of inhaling, because exhaled air is not completely exhausted and waste air is inhaled again. Manufacturers add a breathing valve with an exhaust fan to optimize this failed design, and the exhaust effect was better after the improvement, yet it brought about new problems, such as glazed frost, environmentally unfriendliness, and so on.
When Zhang Zhan, alumnus of the Department of Industrial Design of the Academy of Arts & Design of Tsinghua University, and his team redesigned the masks, aiming to allow users to breathe freely when they wear them. In essence, a mask is only an extension of the human respiratory filtration system. What they do is recreate these two unseen breathing spaces outside the human body with an interlayer closely fitting to the face to separate the space for the mouth and the nose so that the respiratory spaces for each organ becomes smaller. In this case, with the same tidal volume, the positive and negative air pressure fluctuations in each space are larger than those of traditional masks, and the air conversion is accelerated. This is equivalent to a combination of two natural fans, thus maintaining good permeability without any extra material waste. They named the mask “caretaker”, meaning to take care of human breathing.