Back in the 80's, my wife was the primary Health Physicist assigned to radon studies in CDC's radiation studies branch and worked closely to set the public exposure guidelines with EPA.
If memory serves, the exposure guidelines can be viewed in the EPA docs that she coauthored lo' those many years ago. The current EPA guideline docs are at: »www.epa.gov/radon/pubs/index.html I haven't looked at them in a long time and my wife moved into other cancer epidemiology work long ago.
On the EPA's website link you provided there's a PDF there that I went through. It gave me quite a good bit of information. Thank you very much. -- A government big enough to give you everything you want, is strong enough to take everything you have. -MLK
I'm glad the info was useful. My advice is to follow the advice on the CDC and EPA websites. Test the home, and if the guidelines suggest it, assure that remediation mitigation work is done and maintained to reduce the risk of the occupants.
You should search the archives of the Home Improvement forum here with keyword "radon" as I recall there have been some threads where members showed pics of their remediation systems in their homes along with discussions.
Edit: The right term is "mitigation" not "remediation". -- nohup rm -fr /&