If you are interested in finding a qualified radon service professional to test your home or you wish to purchase a radon test kit, the Environmental Protection Agency (EPA) has has a few recommendations and sources to assist you.
Contact your State Radon Contact to determine what are, or whether there are, requirements associated with providing radon measurement and or radon mitigations/reductions in your State. Some States maintain lists of contractors available in their state or they have proficiency programs or requirements of their own. Some states offer free or discounted test kits to the public.