Not medical masks can not prevent new coronavirus, the transmission of new coronavirus is mainly droplet transmission, its droplet diameter is more than 5μm, at this time use medical protective masks, such as medical surgical masks, N95, KN95 masks, sometimes you can also use N90, N99 masks, these masks can stop or filter the droplets with virus, so can play the effect of virus protection. But you can’t use ordinary masks such as cotton gauze mask, sponge mask and activated carbon mask, because the material of these masks is not fine enough, no filter layer, and the gap of the mask is large, so it can’t effectively block the virus and the corresponding droplets. Therefore, ordinary masks cannot be used to prevent viral infections, especially for medical staff working in infection wards, and higher grade N95 masks are often used.