Making a filter out of polyfil

[msarro]

Just curious - I see everywhere about people using in-line HEPA filters for aeration. Would it be possible to build a filter out of polyfil? I ask because in home mycology/mushroom growing (very similar to brewing actually, except way more strict about cleanliness) we use polyfil to make filters all the time. It'd be a whole lot cheaper than buying hepa filters. Tyvek would also work well for covering things where gas exchange is acceptable.