Radon in Middle Tennessee Homes: Testing and Mitigation

Radon is a radioactive gas that forms naturally in soil and seeps into houses through cracks and gaps. You can't see, smell or taste it, and the only way to know your level is to test. Tennessee's environment department says that because of the state's geology, dangerous levels are common in homes, and that radon is the second leading cause of lung cancer in the U.S., after smoking. Testing is cheap or free. Here's how to do it right and what to do with the result.

What the numbers say

• Statewide: the Tennessee Radon Program says 1 in 4 homes that request a free test kit test above 4 picocuries per liter (pCi/L), the EPA's level for immediate action. High levels are more common in East Tennessee, but levels requiring immediate action have been detected in all counties.
• Davidson County: Metro Public Health's radon page says the EPA lists Davidson County as an area with a high potential for elevated radon levels. It reports that about 40 percent of 4,152 homes tested in the county showed elevated levels, and that tests found wide-ranging levels in all areas of the county.

The takeaway is that your neighbor's result doesn't tell you yours. Two houses on the same street can test very differently.

When levels run highest

Metro Health notes the risk rises in winter, when houses are closed up, ventilation drops and radon can build to or above the action level. That makes late fall and winter a sensible time to test, when your result reflects worst-case conditions.

How to test

Get a kit. The Tennessee Radon Program distributes free test kits (it says about 6,000 a year). Order one from its page. Hardware stores sell kits too, and certified professionals can run continuous monitors.

Follow the program's tips. The state lab says it often sees the same mistakes. Its advice:

• run the test for 3 to 5 days only;
• set a reminder to remove it on time;
• record the start and end times accurately;
• mail it back immediately after the test ends (postage is prepaid).

Placement. Follow the kit's instructions on where to put it and whether to keep windows and doors closed. A test in the wrong spot isn't worth much.

Reading the result

The state program summarizes EPA's guidance this way:

The program stresses that no amount of radon is considered safe. A borderline result is worth a second test.

Mitigation: what it is and what it costs

The state program says the most effective way to lower radon is to hire a certified radon mitigation professional, and it points to the national certification directories (NRPP and NRSB) to find one.

The usual fix is active soil depressurization: a pipe and fan that pull soil gas from under the slab or crawl space liner and vent it above the roof. HomeGuide's radon mitigation guide (Feb. 5, 2026) gives:

• typical system: about $1,200 to $2,000 installed, and $2,500+ for larger homes;
• drain-tile suction (for homes with an existing perimeter drain): about $900 to $1,800;
• crawl space sealing as part of the fix: encapsulation runs about $3 to $10 per square foot.

If your house sits on a crawl space, mitigation is often paired with a sealed vapor barrier, which can also help with humidity. See basements and crawl spaces and our encapsulation cost guide.

After installation, retest to confirm the system works. Check now and then that the fan is still running.

Remodeling and radon

• Finishing a basement? Test first. It's much cheaper to put in a mitigation pipe before the walls go up.
• Building an addition on a new slab or crawl space? Ask your builder about radon-resistant construction details while the foundation is open. See home additions.
• Buying a house? Make a radon test part of the inspection.