Having the doors open wont make much difference we are talking tiny dust particles that just float around so small that your lungs cant filter the dust. exhaust extraction is direct onto the exhaust and the outside so NONE of the gases and dust will be floating around the workshop.
i have ordered mine. arrive next week.

sean

http://www.ebay.co.uk/itm/Sealey-Exhaust-Fume-Extraction-System-230V-370W-Twin-Duct-/291446637203?hash=item43db92c293:g:eKsAAOSwuAVWww1f

this kit needs wiring up but in the bigger picture whats a couple of grand for health.