And some 3D mask will use hot-air cotton non-woven fabric for the middle layer in mask. Hot-air non woven fabric is made of ES and low-melting fiber through heating and synthesis, and is also a kind of synthetic fiber filter cotton fabric. Hot air cotton non-woven fabric belongs to a kind of filling material in N95 masks. Hot air cotton non-woven fabric is with high bulkiness, good elasticity, soft hand feeling, strong warmth retention and good air permeability and water permeability. It has the functions of primary filtration, thermal insulation, moisture-proof and improves the comfortable feeling when we wear. Although the hot air cotton non-woven fabric is a filter material, its filtration level can only reach the initial effect of filtration, but it can not replace the "heart" of N95 masks for the meltblown cloth in N95 masks.