There is no shortage of radon related info. on the internet.  You will find everything from naysayers who will tell you that the health risk associated with radon is a myth, to salesmen who wish to peddle their services by way of fear.  The most reasonable point (I believe), lies somewhere in between.  Don't take my word for it.  Go where the science is.  Educate yourself.

Colorado Department of Health & Environment has some excellent radon related resources, including "A citizen's Guide to Radon" (EPA), "Dealing With Radon in Real Estate Transactions", a video produced by the Center for Environmental Research and Technology geared toward real estate professionals, and loads of other good info.

"Basic Radon Facts" is a two page document published by the E.P.A. in 2013.