The existence of charged particles in corona devices is important in electrophotography. Envelope regions where introduced smoke particles cannot penetrate appear around wires on corona discharge in spite of the polarization of the wires. These particles that are initially positive charged keep away from around the wire and collide with the grid electrode on negative corona discharge. With knowledge of particle charging the author shows the motion of charged particles around a corona wire. Numerical calculations correlate well with experimental results. The author defines the generation process of these regions by comparing the initial flow field with numerical simulation results. In addition, the charge quantity of the smoke particles is estimated.