Short-term or long-term radon test: which one do you need?

Start with a short-term test. Most run 2 to 7 days. A long-term test runs 91 days or more and gives a better idea of your year-round average when you are not up against a deadline.

Illinois approves several kinds of test devices. Short-term ones include passive charcoal or electret detectors and continuous radon detectors. Long-term ones include alpha-track detectors and some electret devices. Which one fits depends on why you are testing. Passive devices need separate analysis, and a continuous detector is read a different way.

Buying or selling a home?

A home sale has its own Illinois test rules. Under Appendix B of 32 Ill. Adm. Code Part 422, the test has to run at least 48 hours. There are two ways to do it: two short-term devices set side by side and run at the same time, or a continuous radon detector that records every hour. The test goes in each lowest level of the home that could be lived in. That can mean more than one spot when a home has a basement, crawlspace, or slab section.

IEMA-OHS strongly recommends that every buyer get a radon test before buying or moving in. Because of the sale rules above, many buyers hire a licensed measurement professional. If you hire someone to test, check that they have an active Illinois measurement license. Testing and fixing radon take separate licenses.

The Illinois Radon Awareness Act also requires most sellers to give buyers the state pamphlet and disclosure form, and to share any high test results they have. The law does not make a seller run a new test or put in a system just because the home is for sale.

What if your short-term test is high?

Before you decide on a fix, read what your radon test result means. If you still need a test, our testing page shows how to get a free or $8 county kit.