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Radon is a cancer causing, radioactive gas that you cannot see, smell, or taste. The U.S. Environmental Protection Agency (EPA) states that radon is the second leading cause of lung cancer in the U.S. and the number one cause among non-smokers. Radon comes from the natural breakdown of uranium in soil, rock, and water and finds its way into homes through cracks and holes in the foundation, construction joints, and plumbing fixtures. Any home can have a radon problem. The only way to determine if your home is trapping radon gas is to test.


Test kits can also be purchased from a certified lab or from the National Radon Program. If you purchase a kit from a home improvement store, be sure to check the expiration date. Another option is to hire a radon measurement provider that is certified by one of the two national certification programs, the American Association of Radon Scientists and Technologists, Inc. (AARST) National Radon Proficiency Program or the National Radon Safety Board. The South Carolina Radon Program offers free short-term radon test kits to South Carolina homeowners, subject to availability.

Watch a quick overview of how to use the SC Radon program's short-term test kit. For a successful test, follow the detailed instructions that come with the kit.

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Radon & Lung Cancer

Radon is the second leading cause of lung cancer, after smoking, and the leading cause of lung cancer among nonsmokers. In South Carolina, lung cancer is the most commonly diagnosed form of cancer and the most common cause of cancer deaths. EPA estimates that radon causes more than 21,000 lung cancer deaths in the United States each year. EPA also states that smokers who are exposed to radon have a much higher risk of lung cancer.

U.S. Surgeon General's National Health Advisory

"Indoor radon is the second leading cause of lung cancer in the United States and breathing it over prolonged periods can present a significant health risk to families all over the country. It's important to know that this threat is completely preventable. Radon can be detected with a simple test and fixed through well-established venting techniques."

-  January 2005

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Recommendations for Home Testing

There are two types of radon tests:

  • Short-term tests, which can take as little as a few days depending on the device used, offer a low-cost way to test for radon. Keep in mind that test results can only measure the radon levels in your home during the test period.
  • Long-term tests stay in place for more than 90 days. The results from a long-term test give a better picture of your family's actual radon exposure.

EPA recommendations

Step 1 - Conduct a short-term radon test. If the result is 4 pCi/L or higher, conduct a follow-up test. (Mitigation decisions should not be made based on a single short -term test, regardless of the test result.)

Step 2 -  Follow up with either a long-term test or a second short-term test.

  • For a better understanding of your year-round average radon level, use a long-term test.
  • If you need results quickly, use a second short-term test.

The higher your initial short-term test result, the more certain you can be that you should use a short-term rather than a long-term follow up test. If your first short-term test results were high and you need results quickly, use a second short-term test. If your test result is more than twice EPA's 4 pCi/L action level, you should use a second short-term test immediately.

Step 3 - Evaluate results and take appropriate action.

  • If you followed up with a long-term test: Fix your home if your long-term test result is 4 pCi/L or more.
  • If you followed up with a second short-term test: The higher your short-term results, the more certain you can be that you should fix your home. Consider fixing your home if the average of your first and second test is 4 pCi/L or higher.

Understanding the test results

The amount of radon in your home is measured in pico Curies per liter of air (pCi/L). The EPA recommends that there be no more than 4 pCi/L of radon in your home. This is referred to as the "action level." The action level is the point where the risk of radon exposure justifies the cost of repairs. Because there is no completely safe level of radon, the EPA also recommends that you consider fixing your home if you find radon levels between 2 and 4 pCi/L.

If you make structural or living pattern changes (for example, remodeling or moving to a lower level of your home) you should retest.


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How can I reduce radon in my home?

EPA recommends hiring a radon mitigation contractor that is certified by one of the two national certification programs, the AARST National Radon Proficiency Program or the National Radon Safety Board. Consider obtaining estimates from more than one contractor. More information about selecting a contractor can be found in EPA’s booklet Consumer’s Guide to Radon Reduction.  

For most homes, active soil depressurization, or soil suction, is a cost-effective and reliable technique for reducing radon. It involves collecting the radon from beneath a building before it can enter. Radon levels in most homes can be reduced to 2 pCi/L or below, and most homes can be fixed for about the same cost as other common home repairs. Cost will vary with the reduction method you choose, the size of your house, how your home was built, and many other factors.

If your home has been mitigated, the contractor should provide for a short-term radon measurement to be conducted between 24 hours and 30 days after the system is operational. An additional post-mitigation test kit can be requested from DHEC. It is a good idea to re-test homes that have been mitigated at least every two years. 

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Information for home buyers and sellers of existing homes

EPA has developed a Home Buyer’s and Seller’s Guide to Radon. It is a good idea to have real estate testing conducted by a radon measurement provider that is certified by one of the two national certification programs, the AARST National Radon Proficiency Program or the National Radon Safety Board.

Standards of Practice for both the measurement and mitigation of radon in homes are now viewable online. The Radon Mitigation Consumer Checklist can also be a helpful resource for homebuyers.

DHEC's radon test kits cannot be used for real-estate transactions. Purchasers may request a free test kit from DHEC upon occupancy.

Home building information

Builders and contractors help to reduce residents' risk of lung cancer from exposure to radon when they build radon-resistant new homes. According to the EPA, the cost of radon resistant building is typically less than the cost to mitigate after construction. 

All new homes should be tested after occupancy.

More information about radon resistant new construction (RRNC) is available from the EPA and the National Radon Program. RRNC Standards of Practice are viewable online.

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Radon in water

Radon has also been found in private well water in areas with rocks that contain uranium or radium. If radon is in your well water, it may enter your home and the air you breathe when the water is used for showering and other activities around the house. Water containing radon is typically not a problem in homes served by public water systems. The University of Georgia Agricultural and Environmental Service Laboratories (706-542-7690 or soiltest@uga.edu) offers tests for radon in well water. For more information about radon in water, call EPA's Drinking Water Hotline at 1-800-426-4791.

Historical radon test data

EPA's Radon Zones map shows the areas in the country, including South Carolina, with the highest potential for elevated indoor radon levels. EPA, however, recommends that all homes be tested for radon regardless of geographical location as homes in all three "zones" have been found to trap radon.

View a map of S.C. test results by county. This map is current through May 31, 2020.

Number of tests, average result and highest result by county (Current through May 31, 2020)

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Additional Resources

S.C. DHEC Publications

EPA Publications and Online Information

Other Helpful Web Sites

Radon Standards of Practice

Standards of Practice can be purchased or viewed free online and cover:

  • Single Family Measurement and Mitigation
  • Multifamily Measurement and Mitigation
  • School and Large Building Measurement and Mitigation 
  • New Construction of Homes and Buildings

Useful Telephone Numbers

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Radon Website Survey