If the heat and saliva exhaled from a mask are wet, the function of isolating bacteria will decline, and a new mask needs to be replaced. If you do not use a mask, you can fold it into a beautiful envelope and fold the side close to your nose and mouth inward.
The steps of using masks in one inspection: first, check the color and integrity of the masks, check the light transmittance, and then try to feel, mainly the feeling of the material. If it is too hard or rough, it will be uncomfortable. When buying a mask, smell it to see if there is any peculiar smell. If there is an odor, please do not choose such a mask.
Please carefully check whether the disposable mask is perfect before use. The method of light transmission, that is, care in front of the light, to see whether the light transmittance of the central part is consistent with that of the lampshade. Because disposable masks cannot be washed, they should be discarded after use. Repeated use is not recommended.