Incoming material enters the new Air Grader PB via a laterally positioned airlock and a screw onto the angled perforated screen deck where it is equalized. Air continuously flows from the bottom through the screen, the material and the zig-zag section. The air stream instantly suspends the material acceptable for particleboard production, transports it to the outfeed and onto the cyclone. Large contaminants and coarse materials remain on the screen deck and are discharged. Small impurities (sand, minerals, glass, etc.) fall through the screen deck and are conveyed into the dump.