Corona discharge arrangements for the removal of harmful substances generated by the corona discharge

An improvement in arrangements for removing harmful gaseous substances that are generated by corona discharge in corona discharge apparatus which includes at least one corona electrode (K), at least one target electrode (M), and a d.c. voltage source (2) which is connected between said corona electrode and said target electrode and which has a voltage such as to produce on the corona electrode a corona discharge which will result in the generation of air ions which migrate from eh corona electrode to the target electrode, said arrangement including a suction channel (4) which is restricted relative to he space (1) containing the corona electrode (K) and the target electrode (M) and which has located in the immediate vicinity of the corona electrode (K) an inflow opening (4a) from said space (1), and said channel (4) is operative to conduct the harmful substances to a device (9) for rendering said substances harmless, or to evacuate said harmful substances from said apparatus, wherein said improvements in arrangements includes at least one additional electrode (E) which is connected to a d.c. potential which, in relation to the potential of the corona electrode (k), has the same plurality as the potential of the target electrode (M) and which is mounted in said suction channel (4), or at a location adjacent to said opening, such that an ion current will flow from the corona electrode (K) to the additional electrode (E) and give to an airflow (8) past the corona electrode (K) and into the suction channel (4) through said channel opening (4a).