I'm designing the HVAC for a building that has woodworking and metal shops in it. The wood shop has mills, lathes, various saws/ sanders, etc and the metal shop has welding/cutting/grinding. What is the main strategy for keeping the air clean? Do I put an exhaust above or below each piece of equipment or is it already built in? Do they get a mini-hood or a snorkel-type exhaust? How many cfm? Thanks!