The main difference between the two is where they are certified. N95 masks are approved by the NIOSH and meet U.S. standards. The CDC estimates that 60% of KN95 masks sold in the U.S. are fake.

WSJ put eight N95 and KN95 masks to the test and found not all tested at the required 95% filtration efficiency. Here are experts’ tips for spotting a lesser quality mask. Photo illustration ...