KF94 is one of the grades given to Korean health masks. ‘KF’ stands for ‘Korean Filter’. Korean masks must be certified by the Korea Food & Drug Administration (KFDA) and will be rated KF80/94/99 depending on their performance.1 The numbers quantify the filter performance of the mask.
The higher the KF80/94/99 number, the higher the blocking rate. For example, KF80 blocks more than 80% of the average particle size of 0.6μm and KF94 blocks more than 94% of the average particle size of 0.4μm. Note that masks with higher KF ratings can be harder to breathe as you wear them. Normally, KF certified masks can be purchased for between USD 1.00 and USD 3.00 each. KF certification only guarantees mask filters, so some products that are too inexpensive are not comfortable with the face even if there is no problem with the filter performance. Some masks that can be purchased for more than USD 2.00 are also equipped with a strap adjuster for good close contact with the face.
KF certified masks are basically designed to be worn primarily in places such as dusty places. So make sure you choose the right one for your situation and purpose. On the other hand, it’s important to remember that filters may be degraded by chemicals / oils. It is important to note that if used incorrectly, the high blocking rate of the masks represented by KF certification may not be significant.