The expiration of the mask itself should not have a major impact on the mask material. The filtering effect of the mask itself on bacteria and viruses still exists, and the performance of the mask will not deteriorate due to its expiration. Normally, the performance of the mask does not deteriorate due to the expiration of the mask. However, the expiration of the mask is due to the mask placed too long, too long placed time there may be the possibility that the mask is contaminated or there is bacterial growth, the mask may be the source of pollution, there will be safety risks, to draw attention to. So if you must use expired masks, you need to disinfect the masks according to the method required by the original manufacturer and then use them again. Content source: Dr. You Lai