Air Cyclones are used to remove solids or entrained liquid from a gas stream, or to separate solids from a gas stream based on particle density or size. This Federal Laboratory Unit for Dust Classification was manufactured by Federal Classification Systems, Inc. and includes two copper cyclones in series and a screw auger to meter the solids into the air stream. Two interactive air valves are used to adjust air flow through each cyclone. The objective is to separate a solid sample into two size fractions by optimizing the valve settings. The largest particles are removed by the first cyclone and the remaining particles are removed in the second cyclone. Since the two valve settings are interactive, 2-Factorial DOE is used to design the experiments.