Used masks may carry a large number of microorganisms, such as viruses and bacteria. When wearing a mask people adsorb microorganisms on the outer surface of the mask by inhaling, and touching the outer surface of the mask may cause infection. If the user of the mask carries bacteria and viruses himself, he may also adsorb microorganisms on the inner surface of the mask by inhaling, and infection may occur if others touch the inner surface of the mask. Be careful not to touch other people’s used masks, as cross infection may occur. Individuals should also pay attention to the removal and disposal of masks, and not put them directly into bags, pockets, etc., where there is a risk of continuous infection.