- With an exhalation valve this mask can reduce internal heat, moisture, keep mask always dry. Help people breathe more smoothly and comfortably.- The filtration efficiency (dust-removing rate) of KN95 dust mask is more than 95% for non-oily particulate matter above 0.075 microns.- M-shaped nose clip, dust mask is cut in 3D fits almost any size/shape face, 360° protection. 3D three ...