I bought a 2HP cyclone style collector with cartridge which use at this point, only with my table saw. While I'm reconfiguring the work area I'll be adding the appropriate 6" ducting. Besides the TS, I use a 735 planer and a 6" floor mounted jointer. I will be making collector boxs for the sliding mitre saw, bench top mortiser and drill press. Everything else are portable tools which usually get hooked to a Dust Deputy via the Rockler adapter fittings. I also tend to do much more hand work excepting for dimensioning, so, joinery saws and hand planes.
The wife ordered up a ceiling mounted air cleaner as a present.
I work in an unconditioned space - my 2 car garage of ~400 sq.ft., with open ceilings to the roof, and almost always with the entry door and and the 16' roll-up doors open (well, not in deep winter...). I also wear and Elipse respirator when using any of the machines and for at least 10 minutes afterwards.
My question is about the length of time one keeps the big dust collector "on". Obviously, while using the machine and I keep it on for about 10-15 minutes afterwards, but realistically, with blast gates closed except to the just-used machine, would there be any significant air quality improvement when it's just sucking from the one machine?