1）How to select a qualified mask?
Selection 1: disposable surgical masks, replace it with a new one when it gets contamination or moist.
Selection 2: N95 surgical masks, replace it with a new one when it gets contamination or moist.
Cotton masks or Sponge masks are not recommended
2）The Correct way to wear mask
How to use the surgical mask: the darker surface of mask is the cover which should be wore outward, the lighter surface should be towards to your face. There’s metal strip nose clip on mask, it’s correct if it in on the top edge of the mask, otherwise, it’s wrong. After knowing the front, back, top and bottom of the mask, wash your hands and hang the rope of the mask on your ears. After wearing the mask, press the metal strips on both sides of the bridge of the nose to make the upper end of the mask close to the bridge of the nose. Then pull the mask down so it doesn't get any wrinkles, preferably covering the nose and mouth.