General masks cannot be used after repeated disinfection, because the commonly used disposable surgical masks are made of three layers of materials. The outer layer is a splash-proof waterproof isolation layer, and the innermost layer is a water-absorbing moisture-proof water-absorbing layer. In the middle, the core layer of the mask is meltblown cloth, which can filter small particles of several microns. If the mask is used for more than 4 hours, the filtering function of meltblown cloth will be greatly reduced. Even if alcohol is used to disinfect the mask, it only kills the microorganisms on the surface or inner layer of the mask, and cannot restore the filtering function. Therefore, it is recommended to replace the disposable mask in time within 4-6 hours.