On Sat, 22 Jan 2005 15:16:55 GMT, the inscrutable "Mike S."
spake:

When I'm sanding I have a 20" box fan setup on my bench with 2 filters. I
have the good 3m filter (forget how small a micron it filters but it gets
pretty fine). then I have a cheap fiberglass filter outside of it. I made
like a J-channel for them to sit in then tape the edges to keep it sealed.
Does a pretty good job.

I tried that with a 20" box fan and one paper filter. Airflow
reduction was about 80-90% with the single filter as judged by the
hairs on the back of my hand 8" from the pack of the filter area.
Perhaps the Filtrete filters are less restrictive, but my test failed.


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