NON-IDEAL BEHAVIOR IN CASCADE IMPACTORS.

The study described was with the specific goals of estimating the effects of two non-ideal operating characteristics of impactors on the data obtained with them. These two non-idealities are the lack of step function stage collection characteristics and particle bounce. From the evidence presented, it is suggested that back-up filter catches generally should be omitted from data presentation when dry, non-sticky particulates are sampled. Exceptions should be made only if the MMD is smaller than about 2. 5 mu m. In addition it is suggested that cyclone precollectors having D//5//0's somewhat larger than the first impaction stage D//5//0 be used whenever a non-sticky particulate is sampled.