I wanted to try make an inexpensive ventilation/ exhaust system for my garage. The room is 
roughly 20' x 11' with 7' ceilings. I weld, grind, and use a sandblasting cabinet. My wife
will complain if the house starts to get smelled up from all these processes so i would
open the garage door and the forced air heat from a register i put in from the house would
just go out the door. I bought a 110cfm bathroom exhaust fan from a local home improvement
store for $59.00. I also purchased an electrical box and a single pole on-off switch, a 
scrap piece of 4"pvc pipe, and a dryer outlet wall duct kit. My total cost for all the parts was
around $100. total. I drilled a 4" hole through the cinder block (drilled around the perimeter
and chiselled the rest out) I cut the ends of the pvc with a chop saw so it was nice and cleanly
trimmed. After I mounted the dryer duct kit and caulked around it, i connected the pvc
pipe and screwed it to the ceiling (with anchors i put in first). I rivetted the pipe to the
duct, and to the outlet on the exhaust fan. The final step was to bolt the switch box to the
exhaust fan cabinet and wire with flex conduit. It works pretty good as far as cutting down
some of the dust and smoke without sucking all the heat out of the room. Keeping the Mrs.
happy by spending only $100... priceless.

walt