Abstract: In order to clean the waste gases from a processing system (1), in which a process using non-metal halide is carried out, the waste gas (3) is mixed with a gas (7) that prevents recombination of ionized particles formed from the non-metal fluoride. In a gas discharge chamber (25), the waste gas (3, 7) is then converted into a plasma in which the non-metal halide, present in the waste gas (3, 7), is ionized. The ionized particles, that have been saturated with the gas, prevent the recombination thereof and can then be removed from the waste gas.