It is currently believed that medical surgical masks and N95 masks provide better protection against novel coronaviruses. Since the new coronavirus is a respiratory-transmitted virus, it is important to choose a safe protective mask to prevent infection by the new coronavirus. Although ordinary protective masks can block most of the dust, particles and liquid droplets, they have relatively poor protection against the new coronavirus. Medical surgical masks have reached the level of medical use, its protective effect is better, it is currently believed that medical surgical masks can effectively prevent the new coronavirus through the respiratory tract infection of the organism. N95 masks with exhalation valves, airtightness is better, can also be very good at preventing the virus into the respiratory tract. No matter which kind of mask must be used in the specified effective time, the time limit to discard, usually 6 ~ 8 hours after its protective effect will be greatly reduced.