Re: Air Filter Collection Efficiency

["Otto G. Raabe" <ograabe@ucdavis.edu>]

At 09:42 AM 11/26/97 -0600, you wrote:
>
>Does anyone have any information concerning the change in collection
>efficiency of an air filter as it becomes loaded with dust?  I suspect that
>the collection efficiency increases with dust loading, but to what extent?
>
November 26, 1997
Davis, CA

There is no simple answer to this question, since it depends on the filter
media being used and the size of particles being collected. For
high-efficiency filters (>99% collection at 0.3 micrometer physical
diameter)the main effect of loading is increased resistance of air flow
which reduces the amount of air passing through the filter unless there is
a compensating increase in vacuum applied downstream and efficiency remains
high. For less efficient filters, the loading could increase the efficiency
of collection of particles smaller than 0.5 micrometer in physical diameter
while decreasing efficiency for collection of larger particles.

Otto
		*****************************************************
		Prof. Otto G. Raabe, Ph.D., CHP
                [President, Health Physics Society, 1997-1998]
		Institute of Toxicology & Environmental Health (ITEH)
		     (Street address: Old Davis Road)
		University of California, Davis, CA 95616
		Phone: 530-752-7754     FAX: 530-758-6140
		E-Mail: ograabe@ucdavis.edu
		******************************************************