1. It can be distinguished by observing the metal strips. In order to better fit the face, metal strips are placed in the mask. Generally, the metal strips are located on the top of the mask. If you can clearly see that the side of the metal strip is facing outwards, it is invisible The side of the metal strip faces in.

2. For some individually packaged masks, after opening the packaging bag, if the mask is folded, then the front and back can be distinguished by the crease. Generally speaking, the side with the crease upward is facing inward, and the crease is downward. One side faces outwards.

3. According to the degree of smoothness, because the outer surface of the mask contains water-blocking function, it is mostly smooth, while the inner layer is mostly made of a material with good air permeability, which is close to the skin, which helps to keep breathing smooth, the material is delicate, and the surface is comfortable. Therefore, the inner layer material is less smooth than the outer layer. The smoother side of the mask material faces outward, and the soft side faces inward.

4. By color distinction, the darker side faces outwards, the lighter side faces inwards, and the lighter side has the function of absorbing moisture. It should be close to the nose and mouth, and the darker side facing outwards.