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Appl Environ Microbiol. 1963 September; 11(5): 394-397

Testing Air-Filtering Systems

I. Procedure for Testing High-Efficiency Air Filters on Exhaust Systems

National Animal Disease Laboratory, Animal Disease and Parasite Research Division, Agricultural Research Service, U.S. Department of Agriculture, Ames, Iowa

ABSTRACT

A procedure was developed for evaluating high-efficiency filters mounted in exhaust ducts at the National Animal Disease Laboratory. An aerosol of the test organism, Escherichia coli B T₃ bacteriophage, was generated in a chamber attached to a ceiling exhaust register in concentrations of at least 1000 viable organisms per ft³ of air. Samples were collected from both the pre- and postfilter areas, and the number of organisms per ft³ of air was determined. The efficiency of the filter was calculated from these figures. A total of 269 high-efficiency filters were tested. Of these, 249 had efficiencies of 98% or greater. The remaining 20, with efficiencies of less than 98%, were repaired and retested. No filter was accepted with an efficiency of less than 98%.