GUEST AUTHOR: Ryan Paris, Virginia Department of Health

*This is the second of a 4-part weekly series on radon in real estate

You cannot use radon risk maps or other radon test results in your neighborhood to accurately predict the radon level. The only way to know for sure if radon is a problem in a particular home is to TEST for it. To insure that the test is done correctly, EPA and VDH strongly recommend hiring a certified professional radon tester to conduct the test. Virginia law requires that radon testers be currently certified, and lists may be found at or A professional radon test will cost between $100-200, depending on the test device used. For several reasons, the best test device to use for real estate transactions is a Continuous Radon Monitor (CRM).

The highest indoor radon levels will usually be found in the lowest level of the home, so the lowest level of the home that is finished or easily could be finished should be tested. If the home has multiple sections that are in contact with the ground, these should also be tested—especially if they are on different elevations and/or have a different type of foundation.

The indoor radon levels normally fluctuate with the time of day and the season. Most homes will test at their highest radon levels in the winter and lowest in the summer. Testing during major storms should be avoided. Except for normal exit/entry, the home’s windows and doors should remain shut during the test. The minimum testing period is 48 hours. For other basic Radon Testing protocols, click here.


This information and more is presented in greater detail in 1 or 2 hour CE courses that are designed for Virginia REALTORS®. For more information, click here.