Buying and selling a home: Testing for radon

by Duane Friend

If you are buying or selling a home, here is some information you need to know about radon. This information comes from the University of Illinois Extension website link,, for Take Action on Radon. As of January 2008, the Illinois Radon Awareness Act requires disclosure of all radon test results to potential buyers. It encourages the home owner to test their own residence. The resident of the home may test their own residence, or hire a licensed radon measurement professional. When conducting real estate transactions, using a licensed radon measurement professional is recommended.

Where do you find an Illinois licensed professional to measure for radon?

Contact the Illinois Emergency Management Agency (IEMA) at 800-325-1245 or use their website’s directory of licensed measurement professionals. For more information, please download IEMA’s “Real Estate Testing Guidelines.” The professional will perform a short-term test that lasts 2-7 days. A test must last for a minimum of 48 hours. The measurement professional will test each of the lowest structural areas of the home. If your house has one or more of the following foundation types: basement (test in the basement), crawl space (test the room above the crawl space), and slab-on-grade (test in a room with the slab-on-grade foundation), all three areas must be tested.

When testing, should the house be closed up?

When testing the house, all windows and doors must be closed except for normal entry and exit. Do not operate fans or other machines, which bring air in from outside (except fans that are part of a radon reduction system, or small exhaust fans that operate for only short periods of time.)

Where should the professional place the detector?

  • Choose a place where the detector will not be disturbed.
  • Place the detector three feet from doors and windows to the outside, twenty inches to six feet above the floor, and four inches away from any other objects.

Where should the professional avoid placing the detector?

Don’t place the radon detector in the kitchen, laundry room or bathroom since humidity may affect some detectors. Also avoid crawl spaces, on the floor or by cracks in wall, or next to the sump pump. These locations could cause a false high reading. This location could lead to an inaccurate test result.

What do the results mean?

If your results are less than 4 pCi/L, the USEPA (United States Environmental Protection Agency) action level, no action is needed; however, the buyer should consider re-testing in two years.

What if results are over 4 pCi/L?

When results are over 4pCi/L, the recommendation is to contact a licensed mitigation contractor to reduce radon levels in the home below 4 pCi/L. Carefully interpret the results of the radon test and arrange for any retesting or mitigation, if needed. For more information, visit the Take Action on Radon website.

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About the author

Duane is an Educator with University of Illinois Extension in the Calhoun/Cass/Greene/Morgan/Scott unit.

View all articles by Duane Friend

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