Abstract: A two-stage electrostatic filter includes an ionization section which is arranged in an upstream part of a throughflow passage (28) and includes a wire-like corona electrode (31) which is disposed in an ionization chamber (29) and connected to one pole of an electric high voltage source (16). The filter further includes a target electrode (21;37) which is spaced from the corona electrode (31) and connected to another pole of the high voltage source. A capacitator separator (30) is located in a downstream part of the throughflow passage (28) and includes a first and second group of electrode elements (32,33) which are placed side-by-side in spaced-apart relationship. The electrode elements (32) of the first group are placed alternately with the electrode elements (33) of the second group and are adapted to lie on a potential which is different from the potential on which the electrode elements (33) of the second group lie.

Abstract: An air cleaning apparatus, especially for cleaning of room air, includes an ionizing device (14) having a unipolar ion source formed by a corona discharge electrode, an electrostatic precipitator (12) connected to a high-voltage source (15) and having a flow-through passageway (18) for air to be cleaned and two groups of electrode elements (16, 17) disposed in the flow-through passageway, the electrode elements (16) of one group being interleaved with and spaced from the electrode elements (17) of the other group and arranged to be at a potential different from that of the said other group. The corona discharge electrode (21) is arranged such that the ions generated at the electrode can diffuse essentially freely away from the electrode and thereby diffuse substantially freely throughout the room in which the ionizing device (14) is positioned.