PM2.5 masks cannot be used to protect against coronavirus. First of all, PM25 masks are designed mainly for use in hazy weather, or dusty working environments, particularly dusty, protective masks, it is mainly to isolate the diameter of the fine particles in the 2.5μm or so into the respiratory tract. And the new coronavirus, its diameter is probably in a few nanometers, which is not an order of magnitude, to be more than 1000 times smaller than the micron, the particles are more than 1000 times the difference between the small particles are simply not possible through the PM2.5 mask for protection. Therefore, it is still necessary to wear medical N95 masks, or surgical masks, the efficacy of these masks, as well as the protective effect is very very sure, and can play a very good role in isolating coronavirus, as well as other respiratory pathogenic microorganisms, it is worth the clinical as well as the usual prevention and control of the work of the recommended use.