Abstract: A single field ionizing electrically stimulated filter utilizing a non-conductive filter medium is charged by an electric field created between an ionizer space-apart from the upstream face of the filter media and an electrode placed in close proximity with the downstream face of the filter media. The ionizer and electrode are respectively supplied with differing high voltage potentials. For optimum efficiency, the electrode at least loosely contacts the downstream face of the filter media. HEPA glass filter media in sheet form is pleated and sealingly mounted in a nonconductive frame, with the pleats spaced apart by non-conductive spacer means applied across the filter media faces. The ionizer includes a plurality of ionizer wires extending across a nonconductive frame and spaced back from the frame's downstream face so that gap is maintained between the ionizer wires and the filter medium.