Hi Corel guy. There are several things in your post I don't agree with. First off, not everyone uses the Penn State blower (although not a bad choice), I know several people (including at least 1 laser system manufacturer) who use the 1 hp Grizzly dust collector. Works fine for exhaust and also for vacuum hold-down. I have had one outside in a deck box for 2 years; no moisture, no rust.

Putting the blower next to the laser is the worst place you can put it. Any exhaust gasses between the blower and the outside vent are in a pressurized line, and any leakage is being blown into your building. It is better and safer to have the blower at the end of the run than at the beginning. If the blower is at the end of the run, any leakage on the intake side of the blower will just suck room air into the line and exhaust it outside; it is a negatively pressurized line.

Lastly, you NEVER want to use either of these units for a spray booth application. Neither unit is rated explosion-proof, as they both draw air (and volatile fumes) past the motor. OSHA or your local fire inspector is likely to have a big problem with an installation of this type.