John,
Are you state licensed? In back-asswords Ohio we are and, as such, cannot comment on Radon mitigator's work unless we are also licensed to do mitigation. To get licensed we must attend a class and pass a test, which includes mitigation systems.
I got yelled at by a mitigator one time because I commented on the installation. I simply explained how it was done and what to look for as the occupant of the building. It was a perfectly appropriate installation, but I still got the call. I have since dropped my license and I can say what I damn well please. Obviously, I recommend that guy's competition when I can, just to be helpful.
The EPA site should provide you with all the info you need.
Ed