Been doing them since I was a kid, my mom was a general contractor and she started using Vacuflo in 1976 and our company Vacumaid in 1989. The exhaust was horrendous, which needed to be vented to an outside wall. The static build up attracted the carbon from the motors like crazy all over the piping in the garage.

We presently use Modern Day aka "Silent Master" or other versions they have--pretty much exclusively since 1999. Love that you don't have to exhaust the units if you don't want to. The S5 30amp units are very powerful and reliable and headquartered in So. Cal.