Electret Air Filters

This review summarizes the research progress made so far on electret air filters used for separation of airborne particles from complex air stream. A set of different categories of these filters are delineated and the methods of manufacturing of these filters are described. The principles and mechanisms of filtration and modeling of pressure drop by these filters are analyzed. The filtration performance of these filters is discussed along with their specific advantages and limitations. The reliability of these filters is reported in terms of their charge storage capability. Many interesting inventions as reported on electret air filters in the recent patents are discussed. The latest regulations on air filters are described and how they are driving electret filter research is indicated. Specific research needs are highlighted with a view to further improve the filtration performance and long-term effectiveness of these filters.