Jerry,
George is right, except he meant to say 0.5 micron.
If you want to learn a lot about how to make you shop safe from the fine (dangerous) dust, visit Bill Penz's web site at
Bill's Cyclone Dust Collection Research - Home Page
He has some good information on how to make a system efficient at picking up fines, even if the manufacturer doesn't offer such fine filtration.
Take some time and read through what he has to say and then make your own decision. It was a real eye-opener for me.
I'm tired of blowing sawdust out of my nose, much less the ultra-fines that make it past there and into the lungs.
"Homey's not goin' there no more!"
Jim