PURPOSE: To oxidize soot for lower concentration of exhaust gas produced by an internal combustion engine by applying an alternating voltage or a pulse power to the exhaust gas.
CONSTITUTION: A soot reduction device 2 consists of an outer shell 21 of a conductive material, an exhaust gas inflow port 23 which opens at right angles with the outer shell 21 in the vicinity of a flange 22, and an electrode 24 which is held by an insulator 241 on the center line of the flange 22. With an exhaust gas from a diesel engine carried into the device 2, an alternating voltage is applied between the outer shell 21 and the electrode 24. Air is blasted 50l/min against the periphery of the insulator of the central electrode 24 inside the outer shell 21 so as to prevent electrode's troubles or stain caused by built-up soot. An experience shows that the application of the alternating voltage to the device which is provided for the diesel engine reduces Bosch concentration, representing an exhausted smoke concentration up to about 50%. The total weight of soot is reduced up to about 39%.