An air filter structure is described including a plurality of filter units, wherein a first filter unit made of electrostatically charged fibrous material is utilized at the inlet side of the air filter. The first filter unit has a comparatively greater porosity than the remaining filter units and attracts...http://www.google.es/patents/US4938786?utm_source=gb-gplus-sharePatente US4938786 - Filter for removing smoke and toner dust in electrophotographic/electrostatic recording apparatus
Filter for removing smoke and toner dust in electrophotographic ...
