The collection performance of deep-bed electret filters

Deep-bed electret filters are used to separate fine particles (diameters < 10μm) from gas flows. Compared with conventional deep-bed filters having similiar pressure losses, they operate with substantially higher collection efficiencies. In this paper, two experimental methods allowing the charge characteristics of single electret fibres to be determined, are presented and discussed. Furthermore, the results of the investigated fractional efficiency measurements are given for experiments conducted on two different filter materials, for a particle size range of 10 nm to 10 μm, and at a filter face velocity of 10 cm/s.