With a PLEATED filter, DOUBLING the thickness increases the SURFACE AREA by
about DOUBLE. So, you're actually DOUBLING the SURFACE AREA of the filter,
which effectively HALVES the air flow through each SQUARE FOOT of filter
material. Thus, PERMITS mroe air flow with LESS restriction.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
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"Erma1ina" wrote in message
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It's the CROSS SECTIONAL area that is important in fluid dynamics.
Doubling the amount of material in that CROSS SECTIONAL area will
RESTRICT the flow.