I always recommend that my MD buyers perform their own radon test on a home before purchasing it. Montgomery County, MD actually requires a radon test be performed before settlement and if the buyer isn't willing to do it the seller is required to test and provide a report to the buyer. If sellers are not willing to remediate the radon due to the seller's market we're experiencing, at a minimum the buyers know about it and can take steps to remediate it before they spend any time in the basement.
One company that I recommend to my clients is Roberts Radon in Gaithersburg, MD. They can be found at www.robertsradon.com and they're very professional and competent. I know my clients are in good hands when I point them to this company.
Radon is a killer and as part of the real estate community in Maryland, DC and Virginia, we need to make sure that our clients understand how deadly it can be.