Testing for Radon

You can test the home you live in. When selling your home, consider hiring a licensed radon measurement professional and follow the guidelines set out in IEMA's Radon Testing Guidelines for Real Estate Transactions [PDF]. For more information, visit our page on Buying and Selling a Home.

How To Test Your Home

Testing is easy. First, perform a short term test. Most short term tests take 2-7 days. Allow a minimum of 48 hours for a radon test.

Test for radon in each of the lowest structural areas of the home. If your house has one or more foundation types, a test should be placed in or above each area. For example, if a home has a basement, test in the basement if anyone spends at least 7 hours a week in the basement. If the home has a crawl space, place a radon detector in the room above the crawl space. If the house has a  cement floor, ("slab-on-grade") place a radon detector in any room. Avoid testing in the kitchen, bathroom and laundry room. If a house has all three foundation types, all three areas should be tested for radon.

Where To Find Test Kits

There are different types of short-term radon detectors. Some come in a bag, some in a vial, and some are in a round canister. Download a guide to several common types of detectors. Follow the package directions for the detector you choose. Radon detectors are available for purchase at hardware stores, and from radon measurement laboratories. An Illinois licensed radon measurement professional can also test for radon in your home.

Examing a typical radon test kit.

Conducting the Test

These are general guidelines. Be sure to follow the instructions that come with the detector.

Twelve hours before you test and during the test:

  • Keep all windows and doors 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 do I put the detector?

  • Where the detector will not be disturbed
  • Three feet from doors and windows to the outside
  • Twenty inches to six feet above the floor
  • Four inches away from any other objects
Place the detector according to the guidelines.

Where do I avoid putting 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, the floor, cracks in wall or next to the sump pump. These locations could cause a false high reading. [See the photo below.]

Placing detectors incorrectly can cause false readings.

Once the test is complete, be sure that the start date, stop date and time are listed for the test. Place the detector and other paperwork in the package to send to the laboratory. Seal and mail to the radon measurement laboratory. It usually takes ten days to two weeks to get the results.

Mail in the detector according to its instructions.

Interpreting the Results 

For results less than 4 pCi/L, USEPA’s Action Level, no action is needed. Consider retesting in two years.

If results are close to 4 pCi/L, you may wish to perform a long-term test for a better understanding of your year-round average.

Take Action If Results Are 4 pCi/L or More*

When results are over 4 pCi/L, the recommendation is to perform a second test. If the results are less than 10 pCi/L perform either a short-term or long-term test. If 10 pCi/L or more, perform another short term test.

If the second or average results are above 4 pCi/L, contact a licensed mitigation contractor to reduce radon levels  to below 4 pCi/L.

Carefully interpret the results of the radon test.

Carefully interpret the results of the radon test and arrange for any retesting or mitigation if needed.

*Since there is no safe level of radon, home owners may wish to have a radon mitgation system installed, even if test results show a radon level of less than 4,  to reduce the radon level as much as possible. Today's mitigation systems can often get the radon levels to 2 pCi/L or lower.