When did you have it tested. The inspector told us that levels are usually higher in the winter, due to windows not being open or fans being used. So he said that he wanted it either very low, or over 4. That way when you give the seller the info, they can't say its good when its at 3.8 or so, cause then in the winter it would be over.i have a neighbor that paid someone to mitigate their radon level - haven't seen what they did on the inside, but the outside is just a section of rain gutter running up the center up their house to the roof. I think they paid a few thousand dollars, but not sure. I would also like to hear about some companies that people have used, and what they paid. We had ours tested and it was barely outside of the safe range....