Although the protection level of KN90 masks is not as high as that of KN95 masks, they are still able to meet certain standards. For KN90 masks, although the level of protection is not as high as that of KN95 masks, it is still sufficient to block the spread of droplets, the diameter of which is above 5μm, and there are few droplets smaller than 5μm. Droplets as the main mode of transmission of the new coronavirus, N90, KN90 masks generally refers to a certain flow rate, such as 85L/min flow rate, can block about 90% of the particles above 0.3μm. For 5μm particles, the diameter is almost 20 times that of 0.3μm, so it is almost completely protected. However, it may not be necessary to use a mask with a high level of protection such as N95 or N90 for normal use. If you are not going to a fever clinic or isolation ward, etc., an ordinary medical surgical mask can also provide some protection and protection. Source: Dr. Yurai