On 8/29/2018 10:58 AM, Leon wrote:
....

In the single bag situation the bag acts as the filter and the
collector.Â* With the two bag units the lower bag catches the bulk and
normally does not let air penetrate.Â* It is normally a plastic bag.Â* The
upper bag is strictly the filter/air outlet.Â* Oddly the cloth upper bags
tend to filter better once they get a coating of dust covering the
inside surface.
....

Unless you upgrade or buy upper/top-end unit, run-of-the-mill DC filter
bags are typically 5, 10 or even 30(!) micron so fines are pretty easy
to get by. What _is_ trapped simply blocks some of the open pore area
effectively making it a better filter (with reduced air flow, of course).

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