KN95 masks can play a role in isolating droplets and the new coronavirus. Novel coronavirus pneumonia is a respiratory infectious disease transmitted by droplets and is an acute infectious pneumonia with a new coronavirus as the pathogen. Its diameter is very small, 60-140nm, in the air in the form of aerosols, and KN95 mask can isolate the average diameter of 0.3μm particles, and the particle filtration rate is high, so KN95 mask can play the effect of isolation of the new coronavirus. In general, in public places with high flow of people such as bus and subway, you need to wear KN95 mask, after putting on the mask, you should properly squeeze the metal strip on the inner layer above the mask, so that the mask is close to your face and nose, and if there is air leakage, you should adjust it in time. Although the KN95 mask can isolate the new coronavirus, it cannot completely isolate the virus.