The results of the presented special treatment method indicate a soot decomposition mechanism due to long-living species like ozone and a multistage process between diesel soot and ozone. Measurements inside a dielectric barrier discharge (DBD) and measurements with ozone externally generated show a strong dependence of the decomposition rate on the temperature. In addition the temperature dependence of the lifetime of ozone up to 180 degrees C and the oxidation of carbonmonoxide to carbondioxide were investigated.