An air filtering device for an air conditioner, in particular for filtering out particles, preferably pollutants, from air is provided. The air filtering device comprises a flow path through which air flows along a flow direction, an ionizer for generating ions in the flow path, and grid structure made of an electrically conductive material, that is upstream of the ionizer in the flow path in the flow direction, which forms a first electrode. A filter is downstream of the ionizer in the flow path in the flow direction which has a layer that forms a second electrode. The air filtering device also comprises a high voltage power source that has an electric pole and an electric counter-pole for generating a high voltage between the pole and the counter pole. The pole is electrically connected to the ionizer, or its discharge electrode, and the counter-pole is electrically connected to the first and second electrodes.