The Japanese government is guided by the Japan Ministry of Health, Labour and Welfare (MHLW), with the relevant performance standard being the JMHLW-2000. They outline twelve classes of masks, divided into two groups: replaceable (R) and Disposable (D): RS1, RS2, RS3, RL1, RL2, RL3 and DS1, DS2, DS3, DL1, DL2, DL3.
- The difference between the Type-S masks and the Type-L masks are to indicate the different aerosols that were tested on these masks. The Type-S masks were tested with NaCl aerosols while the Type-L masks were tested with DOP aerosols. The S and L stand for solid and liquid respectively.
- The type-1 masks filter at least 80% of airborne particles; the type-2 masks filter at least 94% of airborne particles and the type-3 at least 99% of airborne particles.