[spthorn60]

As most home woodworkers could confirm, a filter-on-a-box-fan works wonders in a (saw)dusty garage. Even after sanding or sawing MDF, the air is clean after about 10-15 minutes. From personal observation, I'd suggest that non-taped is a good idea, as any non-filtered air is routed through the fan to help overall circulation; ideally you want to displace all the air in the room quickly.

[StavrosK]

How long does it take to clear the air without the filter? I'd imagine sawdust is heavy enough to fall down on its own after a while.

[spthorn60]

Right the heavy stuff falls pretty quickly. The light particles will take quite a long time, and in the meantime, you're potentially breathing all that. I use a large cyclone for the machinery, a filter-on-a-fan, and a mask. My shop is a lot cleaner than it used to be, and I'm sure my lungs are too.

[bluGill]

Sawdust is a mix of particle sizes. http://billpentz.com/woodworking/cyclone/beginnnerscorner.ph... has a ton of information on sawdust.