Radon is a gaseous element that results from the disintegration of minerals in the ground. It occurs naturally, but can be more intense in different areas, even in neighborhoods, or house to house. It is radioactive, and is odorless, colorless and tasteless.
Radon comes into a home through a basement or foundation, seeping through floor joists, or cracks in the floor, cracks in the walls, and gaps around service pipes.
In Western North Carolina we have a higher than normal rate of radon in homes. Henderson and Buncombe Counties are definitely in the red zone (EPA map to the is here).
With Radon being the number two cause of lung cancer, I would advise any home buyer get the test done as part of a Home Inspection. If levels are low, you can move forward. But if testing is high, you will definitely want to get it fixed prior to moving in.
Most Home Inspectors are either qualified to perform a radon test, of work with someone who is. The cost is usually well below $100, so it is definitely worth the money. Testing should show levels below 4.0 piC/l. Anything below is fine. Anything higher should be addressed.
The fix for Radon is not that bad. The cost is around $1500. It involves venting the crawl space or basement through any number of systems. Correction is called mitigation, and you will want to look into mitigation systems
You can research systems for a better understanding of how they work. But basically, they work by pulling air from under the house, and releasing it out through a vent that is a bit higher than the peak in the roof of the house. If the home is a slab or has a basement with a cement floor, a hole may need to be drilled into the cement floor in order to pull air trapped below the home up into the vent. The best way to go is to hire a qualified Mitigation Installer to put the system in. They will install a system that meets the specific needs of the home you are buying, and it will have to be an EPA approved system. And it usually can be put in within a few days.
If you are the buyer, you may want to negotiate the system be paid in full or in part by the sellers. But you really should have the system completed prior to moving in.