Joseph Connors writes:
Bob:

Another factor, Bob, is the shop itself. If your shop is open to the
air, then air quality is less of a concern. These bags collectors with
small 4" pipe are dust pumps, pure and simple. When you watch them
inflate with sunlight in back of them, you can see the cloud of dust
produced.

As far as I'm concerned, you need a large blower with 6" pipe and very
good (.5 micron - certified) filtration.



The size of the pipe is _completely_ orthogonal to the efficacy
of the collector bags. A given collector bag will produce the same
"cloud of dust" irrespective of the size of the ductwork.

So long as the chips and dust are being transported from the
machine to the collector, the size of pipe is far less important
than the quality and weave of the bag.

Typical garage shop, 4" is fine.

scott