Masks are an important line of defense against respiratory infections and can reduce the risk of novel coronavirus infections. Whether the mask fits closely with the human face directly affects the protective effect. After the mask is worn, the five fingers of both hands are slightly bent and brought together, and are fastened to the left and right sides of the mask, and a deep inhalation is performed. If you find that the perimeter of the mask are tightly sucked in the face, the basic wear fit is good, with the head, head down, head up and other actions. On the contrary, it is necessary to re-adjust, if there is still air leakage after repeated debugging, it means that the mask is not suitable for this face type, you should re-pick the mask suitable for your face shape.