How does little KN95 or N95 facemask to prevent the coronavirus? Little mask, do you really understand? What types of masks are there? What's the difference between them? Which mask works best to stop the virus? Do we have to buy N95 masks? Does the N95 exhalation valve reduce protection? This article summarizes eleven questions about masks. I hope that in the season when the virus is raging, we can clear up doubts about masks.Whether from an epidemiological perspective or from a clinical research standpoint, there is already a lot of evidence to prove that wearing a mask correctly can effectively prevent the spread of the virus. The first clinical study was published in the International Journal of Infectious Diseases in 2008. The study concluded that, when used correctly, masks can effectively prevent the spread of the virus [1]. Children with influenza at home, if they can use masks correctly, the family is 80% less likely to be diagnosed with the virus, and in this study, the differences between different masks were small. Another study, published in the Annals of Internal Medicine, reported similar results. Researchers investigated 400 flu patients. They found that the families of these patients had a 70% reduction in the risk of flu if they frequently washed their hands and wore surgical masks [2].