Collection performance of impactor with impaction plate covered with various unwoven fabrics was experimentally studied by using oil mist particles. As a result, it was found that (1) application of high-porosity unwoven fabrics on impaction plate drastically raises the collection efficiency and reduces the 50% cut-off size although it degrades the classification performance, (2) 50% cut-off diameter of impactor with unwoven fabrics is insensitive to the nozzle air velocity, Vn, and the nozzle diameter, W, and it is as small as 1 μm for 15 < Vn < 40 m/s at W = 4. 7 mm, (3) If the pressure drop of a fabric is equal to that of an impactor, the collection efficiency of impactor with the fabric is the same as the filtration efficiency of the fabric.
