KN90 masks provide protection against the new coronavirus pneumonia. The lowest protection level is the single-use surgical mask, that is, the ordinary surgical mask. The difference between N95 and KN95 masks is that N95 is the American standard, KN95 is the Chinese standard, KN95 and N95 have the same protection function, KN90 is also the Chinese protection standard. The protection function of the medical surgical mask is better than the medical surgical mask, which can block 80% of the particles. If you are in a place with heavy pollution, you should change the mask in 2-4 hours. If the virus load in the environment is high, the time interval should be shorter. Content source: Dr. You Lai