If you are protecting against the new coronavirus, it is recommended to replace the 3M protective mask once after 4 hours of cumulative wear. 3M masks can generally be reused, but cannot be washed, disinfected, sterilized, or shared with others, and should be disposed of after one-time use if you are concerned about infectious diseases. When the 3M mask becomes dirty, the parts are damaged or you feel that the breathing resistance has become significantly greater, you should replace it in any case. Reused masks should not be stored in sealed bags, but should be kept in a breathable bag and stored to avoid contamination of the inside of the mask. Unused 3M masks should be stored in their original packaging with a typical shelf life of 3-5 years. When used for oil-based particulate protection, Class R should be used for no more than 8 hours at a time cumulatively; Class P should be used for no more than 40 hours at a time cumulatively, or should be replaced after 30 days of intermittent use cumulatively.