I'm just starting this process now. I'm doing the test this week, although I'm doing the mitigation regardless of levels because it also removes moisture and I've got some mold issues.
I've called a mitigation company that sent me an estimate based upon the work/square footage. He said to go ahead and get a test, that way he can do a post mitigation test and provide a certificate that the radon was reduced. I picked up one of the DIY tests.
I've got to do both the crawl space and a basement, so it adds up, but his quote for the crawl space was $1.25/sq. ft, plus $850 for the basement, unless we discover that the slab wasn't poured over gravel. If there isn't gravel, the cost goes up an extra $300-350, iirc.
I wanted a contractor that was certified by the NEHA and/or NRSB. The guy that did my neighbor's house is no longer in business, so I checked with the NEHA/NRSB sites and Angie's list and came up with these guys:
Radon Abatement Services
Office: 301.718.6200
Estimates: 202.213.6200
E-mail:
info@radonrepair.com
Web:
Radon Abatement Services: Radon Removal Contractor in MD, VA, DC
Hope this helps.