Dusts used for testing air cleaner efficiency

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Various agencies in the last ten years have made tests of the dust separation efficiency of air cleaners designed to protect automobile and truck engines against dust entering by way of the carbureter. Very wide differences between results reported by different persons testing the same cleaner, and in a few cases at different times by the same person for the same cleaner, have suggested a study of the reasons for the differences.

As difference in the character of the dusts used was assumed to be probably the largest single factor producing differences in the results, the work here reported was confined to that phase. The dusts compared were secured from a number of sources. Besides four different kinds of fuller’s earth (a material frequently used for air cleaner testing), three other dusts used by air cleaner manufacturers (one European) were obtained. In addition to these were samples of cement, of various screened dusts, and of the “No.1 standard” used in 1922 and the “No.3 standard” used since 1925 in the air cleaner work at the Experiment Station at Davis, California.