RELIABILITY OF ELECTRET FILTERS

The properties of electret filler materials have been investigated The removal efficiency of electret filter materials used in ventilation f ilters and in room air cleaners has been measured for particle sizes r anging from 0.1 to 5 mum. The results indicate that the efficiency and reliability of an electret filter depend to a great extent on the sta bility of the electrostatic charge in the filter material. It has been found that the efficiency of electret filter material can decrease si gnificantly when exposed to diesel fume aerosol or cigarette smoke aer osol. Arizona road dust aerosol, however, causes only a minor decrease in efficiency. The extensive use of electret filter materials in vent ilation applications should be avoided until the stability and the rel iability of the filtration has been verified by long-term-field tests.