Radon Levels Guide

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How to Test for Radon in Your Home: Step-by-Step Guide

Updated November 2026 · Sources

Testing is the only way to know your home’s radon level, and it is cheap and easy. Here is how the U.S. EPA and Health Canada say to do it.

Short-term vs long-term tests

Short-term testLong-term test
How long2 to 90 daysMore than 90 days (Health Canada: at least 91 days in the heating season)
Common devicesCharcoal canisters, electret ion chambers, continuous monitors, alpha trackAlpha track, electret ion chambers
Best forQuick results, home salesYour year-round average
Typical kit priceAbout $8 to $30 (state agencies)Somewhat more; varies by lab
Sources: EPA Citizen’s Guide to Radon; Health Canada; PA DEP; Shaw Local (Illinois kit prices).

EPA’s testing steps

  1. Take a short-term test. If the result is 4 pCi/L or higher, take a follow-up test to be sure.
  2. Follow up with a long-term test (best picture of the year-round average) or, if you need results quickly, a second short-term test. If the first result is more than 8 pCi/L, do a second short-term test right away.
  3. Decide: fix your home if the long-term result is 4 pCi/L or more, or if the average of two short-term tests is 4 pCi/L or more.

Where to place the test kit

  • In the lowest lived-in level of the home (the basement if it is used often, otherwise the first floor).
  • In a room used regularly, such as a living room, playroom, den or bedroom, but not the kitchen or bathroom.
  • At least 20 inches above the floor, away from drafts, high heat, high humidity and exterior walls.
  • For short-term tests, keep windows and outside doors closed (for 2- to 3-day tests, starting 12 hours before), and avoid testing during severe storms or high winds.

Why the floor matters

Pennsylvania DEP’s records show how much the floor changes the result: 37.3% of 2,645,608 basement tests were at or above 4 pCi/L (median 2.8 pCi/L), compared with 20.4% of first-floor tests (median 1.5) and 15.7% of second-floor tests. See our guide to radon in basements.

Where to get a test kit

  • Hardware stores and online retailers sell short-term and long-term kits; lab analysis is usually included.
  • Many state radon programs offer free or low-cost kits, for example in Colorado, Iowa, Tennessee and New York. Check your state page.
  • For a home sale, hire a certified tester (NRPP or NRSB in the U.S.; C-NRPP in Canada), or a state-licensed tester where required.
  • Compare device types in our radon detectors guide.

Frequently asked questions

How long does a radon test take?

Short-term tests take 2 to 90 days; long-term tests take more than 90 days. Health Canada recommends at least 91 days, during the heating season.

What is the best month to test for radon?

You can test any time, but radon is usually higher in colder months when homes are closed up. Health Canada recommends long-term tests during the heating season.

Should I test on the first floor or in the basement?

Test the lowest level you live in. If you use your basement regularly, test there.

How often should I test for radon?

Retest every few years, after major renovations, and after installing a mitigation system. Pennsylvania DEP recommends testing every two years in homes with a system.

Sources