An air filter unit is provided and contains, at least one ionizer, and at least one filter medium, wherein the at least one ionizer contains at least one discharge electrode, at least one counter-electrode, and at least one voltage source, and wherein the at least one filter medium is downstream of the ionizer, and contains, starting from the upstream side, at least one electret layer, at least one mechanically filtering layer, at least one inner electret layer, and at least one electrically conductive layer. The use of such an air filter unit in a motor vehicle is also provided.