An ion-generator for producing an air flow includes a plurality of rectangularly shaped plate electrodes spaced from one another and respectively lying in planes parallel to the direction of the air flow, such plate electrodes extending perpendicularly to the direction of the air flow, the edge of each plate electrode facing upstream being rounded. There is a plurality of rows of needle electrodes disposed upstream of the plate electrodes and extending perpendicularly to the direction of the air flow, such rows of needle electrodes being respectively associated with and oriented towards the gaps between the plate electrodes, the tips of all the needle electrodes being disposed in a plane perpendicular to the direction of the air flow. There is an electrically conductive rod-shaped support for each row of needle electrodes, such rod-shaped supports being arranged parallel to the rounded edges of the plate electrodes. An electrically insulating material covers each rod-shaped support and its associated row of needle electrodes except for the tip of each needle electrode. The plate electrodes are connected to one terminal of a high-voltage d.c. source; and the rod-shaped supports are connected to the other terminal of such d.c. source.