Determine the risk. Most states have large areas where the radon risk is moderate to high, but radon levels can vary significantly even from one house to the next. The only way to know the level in your home is to test, and after you’ve done major structural renovations, test again.

Find a qualified pro. Radon-removal systems can cut the level to 2 pCi/L or lower, says the EPA. They cost $800 to $2,500, or about $1,200 for an average house. Find a trained pro at www.epa.gov/radon or by contacting your state radon office.