There is only one correct way to wear a mask. The correct way to wear a mask is to wear it squarely, that is, with the colored side (usually green, blue or pink) facing outward and the white or light-colored side facing inward. At the same time, the folds should be pulled up and down so that the mask covers the mouth, nose and jaw. Place the fingertips of both hands along the metal strip of the nose bridge and press slowly from the center to the sides to fit the bridge of the nose. Finally, adjust the mask so that its perimeter is fully fitted to the face. If the mask is changed to another side for further use, it will allow the harmful germs that have been blocked by the mask to be inhaled again. In addition, the mask needs to be replaced once every 2-4 hours, and if it becomes wet or stained with secretions, it should also be replaced.