You may want to test again sometime in the future if you living patterns change or if a lower level becomes occupied, then test in that level. Depending upon the type of test you took, you should either test again or fix your home. Individuals at the RIC can give you more information, including a list of EPA approved radon contractors who can fix, or help you develop a plan for fixing, the radon problem. This is a toll-free number operated by the Consumer Federation of America, a nonprofit consumer organization. No level of Radon is considered absolutely safe.
L is the lowest achievable level.
While in some cases you can treat the problem yourself, you should always consider the use of trained Radon reduction personnel who have passed a test and been listed by a Radon Proficiency Program. Such radon mitigation contractors working in Wisconsin are on a Radon Mitigation Contractor Proficiency list for the state. Soil Depressurization is usually highly effective. It has been sent to all public libraries in Wisconsin. However, experience has shown that sealing cracks and openings in basements will not often reduce indoor Radon levels by much.