The good filtering effect of KN95 mask is closely related to its multi-layer fabric and side face fit design. Disposable masks usually only have 3 layers of fabric. KN95 masks have 5 layers of fabric. Two more layers of fabric can prevent air from passing through. The mask goes inside.
Secondly, the side face design of the KN95 mask fits perfectly with the face without any gaps. After pinching the nose wire above the mask to fit the bridge of the nose, air can only enter the human respiratory tract through the five-layer fabric on the front of the mask. The protective effect of sex mask is good. Then, because air can only enter and exit through the mask, and the air permeability of the 5-layer fabric is twice that of the 3-layer, it will be much more stuffy than disposable masks.