Medical protective masks, it is recommended to replace once in four hours. medical protective masks are the most commonly used masks in the clinic, if not replaced for a long time, it will make the dust in the air block the gaps inside the mask, affecting the permeability of the mask, leading to a wet mask, which does not play a role in isolating the virus. n95 masks can be worn for a relatively longer period of time, about six hours. If the mask is not replaced in time, it can directly affect breathing and also easily lead to skin allergies. Not replacing it for more than eight hours will lead to increased humidity in the mouth, which is ideal for the reproduction of bacteria and can easily lead to infection of respiratory diseases. Wearing a mask in life can prevent many respiratory transmitted diseases, such as influenza, neoconiosis, tuberculosis, etc. Therefore, we remind everyone to wear masks properly and actively prevent respiratory transmitted diseases.