Abstract: A filter apparatus of the present invention includes a filter housing having an inlet and an outlet and a filter device locatable therebetween. The filter device includes a filter medium, an electrically conductive screen or mesh, and a conductor for supplying high voltage power. The conductor abuts the filter medium such that when the conductor is subject to a high voltage, the filter medium is polarized and nothing, apart from air or a support or retention material of dielectric material, is on a side of the filter medium immediately opposite to the conductor and no other charge applying device is located upstream of the conductor.