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Radon Test Kits: Short-Term vs Long-Term and How to Test Correctly

Updated November 1, 2026 · General information, not medical advice

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EPA and the Surgeon General recommend testing all homes below the third floor. EPA estimates nearly 1 out of every 15 U.S. homes has an elevated radon level, and says you cannot guess yours from a neighbor's result.

Short-term vs long-term tests

Source: EPA, A Citizen's Guide to Radon, and Home Buyer's and Seller's Guide to Radon.

EPA's three testing steps

1. Take a short-term test. If the result is 4 pCi/L or higher, take a follow-up test.
2. Follow up. Use a long-term test for a better view of your year-round average, or a second short-term test if you need results quickly. If the first result is more than twice 4 pCi/L, take the second short-term test immediately.
3. Decide. After a long-term test, fix your home if the result is 4 pCi/L or more. After a second short-term test, consider fixing if the average of the two is 4 pCi/L or higher.

Already have a number? Use our result checker.

How to test correctly (EPA)

1. Follow the instructions in your kit. They come first.
2. Close windows and outside doors and keep them closed as much as possible during a short-term test. Do not run fans or machines that bring in outside air. For a 2 or 3 day test, close them at least 12 hours before you start.
3. Pick the spot. Use the lowest lived-in level of the home. Choose a room you use regularly, such as a living room, den or bedroom, but not the kitchen or bathroom.
4. Place the kit at least 20 inches above the floor, where it will not be disturbed, away from drafts, high heat, high humidity and exterior walls.
5. Leave it as long as the package says. Do not move it. Write down the start and stop times.
6. Reseal the package and send it to the lab right away. Use the lab named on the package.

Where to get a kit and what it costs

EPA says many radon test kits are sold online and in home improvement stores. EPA's National Radon Program Services at Kansas State University offers discounted kits online. Some state radon programs also offer free or discounted kits, and they can point you to a qualified tester if you would rather hire one.

Pennsylvania's Department of Environmental Protection says kits typically cost about $20 to $30 there and are analyzed by a state-certified lab. We did not find a national price from a government source, so prices elsewhere may differ.

Common questions

How long does a radon test take?

EPA says all radon tests should run at least 48 hours, and some devices need longer. Short-term tests stay in the home from 2 to 90 days depending on the device. Long-term tests stay more than 90 days. Then you mail the kit to the lab, and EPA says results come back in a few days to a few weeks.

When is the best time to test?

Pennsylvania's Department of Environmental Protection says the best time to test is during the colder months, when homes are closed up and radon is most likely to build up. EPA also says not to run a short-term test of 2 or 3 days during unusually severe storms or high winds.

Can I use my neighbor's result?

No. EPA says radon levels can vary greatly from home to home, and homes next to each other can have different levels. The only way to know your level is to test your own home.

Do I need to test again?

EPA says to retest if you start using a lower level of the home, such as a basement, and after major renovations. It also says that even with a result below 4 pCi/L, you may want to test again sometime in the future.

Related guides

• What does my radon test result mean?
• Digital radon detectors vs test kits
• Radon testing in a home sale
• What radon is and the health risk
• Are radon levels higher in winter?
• Order a radon test kit