The N ,R ,P and P categories of masks are stipulated by NIOSH (National Institute of Occupational Safety and Health) respiratory protective equipment standard certification 42CFR-84.

N class is suitable for filtering non-oily particles;

Class R is suitable for filtering oily and non-oily particles, but the use time for oily particles should not exceed 8 hours.

Class P is suitable for filtering oily and non-oily particles. When it is used for oily particles, the service time shall refer to the manufacturer's suggestion. It is suggested that the cumulative service time of 3M shall not exceed 40 hours or 30 days after the start of use, whichever comes earlier.

Common non-oily particles include dust, acid mist, paint mist and microorganisms. Suspended particles in daily air pollution are mostly non-oily. Oily particulate matter includes soot, oil mist, asphalt smoke, particulate matter in diesel engine exhaust, etc.

About Class P masks: At present, the KP masks sold by 3M include 3M 8577 and 8576, both of which are of KP95 grade in China, and they are also certified by NIOSH P95 grade in the United States.

I hope the above reply will satisfy you! If you still have questions, please feel free to ask the enterprise.