N series: protective non-oily suspended particles with no time limit
R series: protective non-oily suspended particles and oil aerosols khan time limit for eight hours
P series: protective non-oily suspended particles and oil aerosols khan has no time limit
When some carrier of particulate matter is oily, and these will reduce electrical material attached to the electrostatic non-woven, make the tiny dust penetration, thus to prevent oil aerosol filter material through special electrostatic processing, in order to achieve the purpose of the tiny dust prevention. So each series is divided into three levels: 95%, 99%, 99.97% (referred to as 95,99,100), so a total of nine small kind of filter material.