@merpreb Merry - N-95 are certified in the US. KN-95 masks are certified in China, supposed to be to the same standards as in the US, so they should be equivalent. They wear the double masks as an extra precaution to protect the KN-95 from contamination by patient droplets while their masks are off for cleaning & dental procedures. So far, so good for them - it has been 10 weeks since reopening, and no one on the staff has been infected.
However, the N-95 industrial masks with the exhaust port, like I wear when working with soil, are not meant to be used for Covid-19 protection of other people, because the port allows droplets to escape while preventing inhalation of particles (it's why they are more comfortable than medical N-95 masks - moisture doesn't build up in them.)
Sue

The N95 and KN95s are supposed to be the same. But China doesn't have the same quality control as the United States. That's just reality. The same is true with baby formula and stuff like that. It's so important to find a reliable source for KN95s so that they are real and not fakes. I think the best sources are people that have been importing them and stocking them in the United States for awhile. They are the people that do the testing to make sure the masks are real and not fakes.