Medical N95 masks can be used for 4 hours. N95 masks are double-blocking masks, and because there is a breathing valve, the disinfection capacity also has a certain limit and cannot be applied in an unlimited cycle. If you feel that the mask is not breathable and getting stuffy during the application process, you need to change it in time. When wearing the mask also do not use your hands to directly touch the inner layer of the mask, at the same time after using the mask can not be directly exposed to the air, to put the mask upside down. Usually medical N95 masks are not able to take medicine for spraying disinfection or cleaning like cotton masks at home, and the application should be defined in accordance with the instructions and use period of the mask, and not for cyclic application.