Class A - charcoal filtration. Removing oil vapor and odors carbohydrate, ensuring maximum remaining oil content of <0.003 mg / m (excluding methane) at 21 ° C. (If the upstream filter class H).
Class H - Highly effective oil filtration. Removal of particles having a particle size of 0.01 micron including water and oil aerosols, maximizing the remaining contents of the aerosol of 0.01 mg / m (<0.01 parts per million) at 21 ° C. (If the upstream filter class G).
Class G - Universal protection. Removal of particles of 1 micron in size, including the condensed liquid water and oil to ensure maximum remaining aerosol content of 0.6 mg / m (<0.6 parts per million) at 21 ° C.
Class D - dust filtration for general use. BSPT filters: Removing dust particles size up to 1 micron. Flange filters: Removing dust particles size up to 5 micron.