Medical Surgical Face Mask

Masks are difficult to buy. This has been the hottest topic recently. Many people can't buy masks, let alone KN95 masks. Some people may buy foreign masks, such as masks in the United States, masks in Japan, masks in South Korea, and different standards for masks in different countries, such as FFP2, FFP3, KF94, N95, KN95, KN90, DS2 various mask standards, So which one is better?
Classification criteria:
FFP3> FFP2> N95 = KN95 = DS2> KF94> KN90> FFP1