Please see the operational bulletin (below) regarding counterfeit KN95 masks that have entered the marketplace. While authentic KN95 masks have been approved as acceptable alternatives to an N95 by NIOSH and the FDA, it is imperative to make sure that if you are using KN95s that they are listed on the FDA's approved list and that they pass qualitative fit tests.
2020-04-18-01 Counterfeit KN95 Mask Advisory (PDF) (4/18/2020)