I am working on floorplans/ layouts for the new building, and am kind of leaning twords wanting a separate  room  for grinding. While I only have 3 at the moment I will likely have a half dozen, possibly more belt grinders shortly. All my scribbling on graph paper it looks like a 14x18 would be about right. With two buffers and 4-6 grinders and a bench or two. Anybody who has gone this route have any advice? 

Covers for all the grinders and especially the buffers to prevent cross contamination when using them for different grits!

Setup for a positive pressure grinding mask

Well sealing cabinet for buffing compounds/buffs (each shelf dedicated to a buff and the compound used on it).

Strong ventilation to clear the air.  A dust collector designed for grinding metal highly suggested!

I was just talking last week with Dereck Glaser of the New England School of Metalwork, and he told me they were planning to incorporate downdraft tables into their grinding area, to remove as much grit and dust as possible.

That's fantastic. I would think a combination down/side draft would work even better. Somewhere to point the shower!