Abstract: The invention provides a filter structure for use with a high voltage power pack for filtering particulates from a stream of air passing through the filter structure. The structure includes a structural element for facing the stream of air and the back parallel and spaced from the front, the front and back defining a plurality of openings permitting a flow of air through the element. A planar insulating substrate is positioned adjacent the front of the structural element and has openings aligned with the openings in the structural element and a plurality of conductors are carried by the substrate about the openings for charging by the power pack. As a result, an electrostatic field is created across the openings orthogonally with respect to the flow of air between the conductors. A non-conductive filter element is positioned in contact with the conductors and between the conductors and the back of the structural element.