3M masks are maintenance-free masks, not disposable masks, can be reused, but can not be washed, wait until breathing is blocked or the mask is dirty to be abandoned and no longer used. Under normal circumstances 3M masks can be used for 3-7 days, without valve masks generally 2-3 days, with valve masks up to 1 week, but also according to the degree of pollution of the specific environment to see. In the following cases, 3M masks should be discarded: 1, the mask adsorbed particles are too high, the user obviously feel breathing obstruction; 2, parts damage, aging, broken or failure, such as headband broken, become loose, nose clip broken, fall off, mask body broken, deformation, etc.; 3, the mask is contaminated, such as liquid spatter, etc.