My $0.02 worth:

Dean Ing wrote an "entertainment" novel about a post-nuke america, can't remember the title right now. In it he describes sealing off the basement of an old house, and providing positve pressure FILTERED air through a carboard/plastic sheet/duct tape bellows--the filter element being a separate box connected via a plastic sheet tube. Filter element was toilet paper rolls, air drawn sideways thru the rolls (center tube being plugged up).

Simple, dirt cheap, and infallible as long as you have enough folks to pull shifts pumping air <img src="images/graemlins/smile.gif" alt="" />

Oh...! Just rememberd name of book: Pulling Through.
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