3M KN9002 mask is an industrial particulate protection mask, its barrier efficiency is not as good as N95 and KN95 , but for the general public, if not in close contact with infected people, for the new coronavirus protection has been sufficient. Because N95 and KN95 masks are in short supply, expensive, and relatively difficult to purchase, KN90 can be used instead. If you go to a crowded closed place, try to still choose medical surgical masks, medical care masks, N95 and KN95 masks, which can play a more effective protective role.