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Home Measurement

Guidelines for Home Environment Radon Measurements

The Illinois Emergency Management Agency(IEMA)-Division of Nuclear Safety has developed protocols for homeowners who wish to test their homes for the presence of naturally occurring radon gas. These testing protocols are summarized in simplified form in the table below. This summarized protocol applies to both residents testing their own dwellings and to professional measurement licensees testing home environments. The testing options outlined are intended to be used by the homeowner to determine if steps should be taken to reduce the radon concentration in the home.

Because of the unique nature of real estate transactions, the IEMA-Division of Nuclear Safety has designed special protocols for radon testing in real estate transactions. If you expect to be selling your house in the near future, we recommend that you contact the IEMA-Division of Nuclear Safety Radon Program for a copy of their fact sheet, “Radon Testing Guidelines for Real Estate Transactions.”

Steps for Homeowner Radon Testing

Test Initial Test Results and Follow-up Tests Test Results:
Do You Take Action?
Conduct an initial short term* radon test in each of the lowest structural areas of the home
If your initial short-term test is:
  • Below 4 picoCuries per liter (pCi/L)
  • No action is necessary. You may want to re-test at some time in the future
  • Between 4 and 8 pCi/L. Follow up with a long-term test**
  • If the average of the two tests is
    4pCi/L or greater, the IEMA-Division
    of Nuclear Safety recommends reducing
    the radon level
  • 8 pCi/L or greater, follow up with another short-term test.
  • If the follow-up result is in agreement
    with the initial result***, the IEMA Division of Nuclear Safety recommends
    reducing the radon level.

* Short-term tests may last between two and 90 days. Most last between two and seven days. Tests between seven and 90 days are usually impractical for real estate transactions, but are fine for homeowners assessing their own radon situation.

Examples of short-term detectors include: activated charcoal canisters, charcoal liquid scintillation vials, electret chambers and continuous radon monitors.

** Long-term tests last between 91 and 365 days, and are strongly recommended by the IEMA-Division of Nuclear Safety for all homeowner (that is, non-real estate transaction) testing. Long-term tests give a better estimate of the year-round radon concentration in the home. The closer the test duration is to a full year, the closer the test result will be to the actual average.

An example of a long-term test is an alpha track detector.

*** If your first and second short-term tests are not in agreement (or if you’re not sure whether or not they agree), contact the IEMA-Division of Nuclear Safety Radon Program or your registered radon measurement professional. You will probably want to conduct a long-term test, or have a radon professional conduct testing to confirm your radon levels. An example of radon measurements that are “in agreement” is a result of 11 pCi/L on the first test and 9 pCi/L on the second. An example of measurements not in agreement is 15 pCi/L on the first test and 2 pCi/L on the second. Radon levels do vary from day to day, but rarely by more than a few pCi/L.

IEMA-Division of Nuclear Safety Recommendations for Homeowner Radon Measurements

• Hire an IEMA-Division of Nuclear Safety-licensed radon measurement professional.
• Be sure that IEMA-Division of Nuclear Safety radon testing protocols are followed.
• Use tamper indicators on all windows and doors not used for normal entry and exit during short-term tests.
• Conduct a long-term radon test, the longer the better, up to one year.
• Call the IEMA-Division of Nuclear Safety Radon Program if you are uncertain about anything regarding radon testing.

Where Test Kits Can Be Purchased…

Short-term and long-term test kits can be purchased at most hardware and department stores, and some other stores. The IEMA-Division of Nuclear Safety Radon Program can provide a list of licensed radon measurement professionals, and a list of businesses which offer testing kits through the mail.

When Testing…

Be aware that any tests lasting less than a week (that is, most short-term tests) require closed-house conditions. Closed-house conditions mean keeping all windows closed, keeping doors closed except for normal entry and exit, and not operating fans or other machines which bring air in from outside (except for fans that are part of a radon reduction system, or small exhaust fans that operate for only short periods of time).

• Before Testing: Begin closed-house conditions at least 12 hours before the start of the short-term test.
• During Testing: Maintain closed-house conditions during the entire duration of the short term test, especially for tests less than one week in duration. Operate home heating or cooling systems normally during the test. For tests lasting less than one week, only operate air conditioning units that recirculate interior air.

Where the test should be conducted…

Place the detector or detectors in the lowest level containing a room that is used regularly, such as:

• a family room, living room, den, playroom, or bedroom; and/or

• in the lowest level suitable for occupancy, even if it isn’t currently used but could be, without renovating.


• in kitchen, laundry room and bathroom (because fan systems and humidity may affect some detectors); or

• in crawl spaces, on floor or wall cracks, or right next to a sump pump, as this may cause a false high reading.

The detector should be placed:

• in an area where it will not be disturbed;
• at least three feet from doors and windows to the outside;
• at least one foot from exterior walls;
• twenty to thirty inches away from the floor;
• four inches away from other objects horizontally and directly above the detector;
• away from drafts; and
• away from heat, fireplaces, furnaces, direct sunlight and areas of high humidity.

If the test results show radon levels above 4 pCi/L…

Call the IEMA-Division of Nuclear Safety Radon Program. Staff there can provide you with names and addresses of licensed mitigation professionals that are trained to reduce radon levels. If you prefer, the IEMA-Division of Nuclear Safety can provide you information on how to fix the radon problem yourself.

After a radon reduction system is installed…

Perform another short-term test, following the IEMA-Division of Nuclear Safety protocols outlined here, to ensure that the radon reduction system is effective. Make sure the system is operating during the entire test.

The IEMA-Division of Nuclear Safety Radon Program can provide:

• Information about radon and radon testing;
• Names of licensed radon measurement professionals;
• Names of licensed radon mitigation professionals trained to reduce radon.

Additional information about radon measurement and mitigation
can be found in your local library.
Call the IEMA-Division of Nuclear Safety Radon Program at: 1(800) 325-1245