N95 and so on, that's the mask level. The N series of masks is the American standard, the KN series is the Chinese standard, the FFP series is the European standard, and the KF series is the South Korean standard.

The following figure refers to the protection ability, the higher the protection level is. The diameter of the water molecule in the presence of gas is about 0.4nm, and the particle diameter of the coronavirus as a whole is about 60-400nm. The mask cannot pass through the larger particle diameter, so it can block the virus. Ninety-five refers to the efficiency of filtering this kind of particulate matter up to ninety-five percent. The 90 series does not have the high protection rating of 95, but it can resist more than 90 percent of particulate matter. In FFP series, 2 basically corresponds to 95,3, and the filtering efficiency is higher, reaching 99%.

The filtering power is represented by the following set of relationships, which is easier to understand: FFP3 > FFP2=N95=KN95=KF94 > KN90. In addition, a number with a V at the end indicates a breathing valve.

To protect against viruses and influenza, the N95 series is sufficient. Medical N95 masks need to prevent high pressure liquid spillage, so the standard is higher than normal N95.

N95, KN95, FFP2 mask certification level

N95 is a U.S. respirator certified by the National Institute for Occupational Safety and Health (NIOSH). N95-certified respirators are at least 95% efficient at filtering non-oily particulate matter, and masks must be labeled "NIOSH" and "N95."

KN95 is a respirator certification class conforming to the Chinese mandatory standard GB2626-2006. Respirators certified by KN95 have a filtering efficiency of no less than 95% for non-oily particles, and masks must be marked with the words "GB2626-2006 KN95".

FFP2 is a CE rating for respirators that meets the European EN149 standard. Respirators certified by FFP2 have a filtering efficiency of at least 94% for oily and non-oily particles, and masks must be labeled with the words EN 149:2001+A1:2009 FFP2.

In addition, surgical masks, the common standard is YY0469-2010 or YY0469-2011, which is printed on the separate packaging of each mask.

All of these respirators (respirators) are designed to be close to the face so that air leaks through the filter material rather than through the edges of the respirator. All certified masks are manufactured within a defined quality standard system.