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Radon In Real Estate

Radon Testing Guidelines for Real Estate Transactions
Because of the unique nature of real estate transactions, which involve multiple parties and financial interests, the U.S. Environmental Protection Agency (U.S. EPA) designed special protocols for radon testing in real estate transactions, which the Illinois Emergency Management Agency(IEMA)-Division of Nuclear Safety has adapted to conform with its radon regulations. These options are listed in simplified form in the table below. If you do not reside in the home being sold, you may need the full protocol, contact the IEMA Radon Program for a copy of the regulations.


Test Options for Real Estate Transactions…

If you reside in the home and may sell but are not currently in a real estate transaction, and you have at least a few months before you expect to be involved in a real estate transaction, you might want to consider home environment testing for radon. See our fact sheet, “Guidelines for Home Environment Radon Measurements.”


What to Look for in Short-Term* Real Estate Testing Options


What to do Next


Detector Location



Two tests, 48 hours or longer, performed at the same time
Two detectors, four inches apart, in the lowest livable level, or buyer’s preference (if buyer exists). Fix the home if the average of the two tests is 4 picoCuries per liter (pCi/L) or more.
Single Test
One test, 48 hours or longer, performed with an active continuous monitor that integrates and records radon levels hourly.
Continuous monitor placed in lowest livable level, or buyer’s preference. Fix the home if the average radon level is 4 pCi/L or more.

* 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.

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

If your tests don’t agree, contact the IEMA…

If your simultaneous or sequential tests are not in agreement (or if you’re not sure whether or not they agree), contact the IEMA Radon Program or your licensed radon measurement professional. While the following table contains examples developed for simultaneous tests, the same general rules apply to sequential tests.

Tampering with radon tests or mitigation systems is illegal in Illinois and carries expensive penalties.

Interpreting Two-Detector Test Results–Are They “In Agreement?”

Both tests below 4 pCi/L One above and one below Both tests above 4 pCi/L
2 pCi/L and 3 pCi/L–
Are in Agreement
3 pCi/L and 5pCi/L–
Are in Agreement
7 pCi/L and 8pCi/L–
Are in Agreement
1 pCi/L and 3.5 pCi/L–
Not in Agreement
3 pCi/L and 7 pCi/L–
Not in Agreement
17 pCi/L and 36 pCi/L–
Not in Agreement

IEMA Recommendations for Real Estate Radon Measurements

• Hire an IEMA-licensed radon measurement professional.

• Be sure that IEMA radon testing protocols are followed.

• Use tamper indicators on all windows and doors not used for normal entry and exit.

• Call the IEMA Radon Program if you are uncertain about anything regarding radon testing.


The Disclosure Act…

The Illinois Real Property Disclosure Act, effective October 1994, requires that a home seller disclose any knowledge about radon levels in the home. The act does not require that testing or remediation work be conducted. However, many relocation companies and lending institutions, as well as home buyers, request a radon test when purchasing a house. Sellers and brokers are cautioned to err on the side of full disclosure of material facts prior to entering into a purchase agreement.


When Testing…

Be aware that any test lasting less than a week requires 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 or levels 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.

For instance, if the house has one or more of the following foundations: basement, crawl space, slab-on-grade; a test, in accordance with this protocol, in each area is necessary.


• in the 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
• 4 feet from heat, fireplaces, furnaces, and away from direct sunlight and areas of high humidity.


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

Call the IEMA Radon Program. Staff there can provide you with names and addresses of professional radon mitigators who are trained to reduce radon levels. If you reside in the dwelling, the IEMA can provide you information on how to fix the radon problem yourself. Measurement professionals are precluded, by rule, from performing mitigation at the same address they have performed a measurement.


After a radon reduction system is installed…

Perform an independent short-term test, following the IEMA protocols outlined here, to ensure that the reduction system is effective. Make sure the system is operating during the entire test.

The IEMA 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 Radon Program at: 1(800) 325-1245