UPDATED 2020

The Radon Test Guide

The Radon Test Summary
What: Radon tests measure dangerous levels of radon in homes.
Who: Homeowners can order test kits from qualified laboratories or hire a professional radon tester.
Where: Radon tests are done inside a home, away from exterior walls, at least 20 inches from the ground.
When: A radon test can be done at any time. Homeowners typically conduct a radon test when they are preparing to sell their home.
How: A testing device measures the levels of picoCuries per liter of air, or pCi/L.
Type: Radon levels are tested with either a passive or active radon testing device.
Why: One in 15 houses in the country has elevated levels of radon. Radon causes 21,000 lung cancer deaths each year.
Time: A radon test can be completed in anywhere from two to 90 days.
Language: English and Spanish
Preparation: Windows and doors should be closed for at least 12 hours before starting a radon test.
Cost: Self-tests range from $10 to more than $100. Professional radon testers charge anywhere from around $50 to over $300.

Radon is an invisible, odorless, tasteless gas that is found in homes. Radon is estimated to be responsible for 21,000 lung cancer deaths annually, according to the Environmental Protection Agency (EPA). The EPA and the Surgeon General recommend that all houses be tested for radon. Homes are most often tested for radon when they are being sold, but can be tested at any time.

Why Test for Radon?

One in 15 houses in the country has elevated levels of radon. Radon is a natural, radioactive gas that develops as uranium breaks down in soil, rocks and water. It then seeps into homes through well water and holes and cracks in the foundation and becomes trapped inside the home. All homes are susceptible to radon, regardless of their age, the presence or lack of a basement, or how well they are sealed. Not only is radon responsible for 21,000 lung cancer deaths each year, but it is the second-leading cause of lung cancer in the US. Every member of a family living in a home with elevated radon levels is at risk. Fortunately, high radon levels can be remedied in a home.

In-home radon levels average around 1.3 pCi/L, or picoCuries per liter of air, while outside air generally has about 0.4 pCi/L. Levels that exceed 4 pCi/L are considered dangerous and should be corrected. Radon levels may also be reported as working levels, or WL. Working levels of .02 are considered too high.

How Does the Test Work?

Radon levels are tested with either a passive or active radon testing device. Passive testers do not require power and include alpha-track detectors, charcoal canisters, charcoal liquid scintillation devices and electret ion chamber detectors. They are left in the home for a specified number of days – tests are either short term or long term – and then sent off for analysis. Active testers rely on power and include continuous working-level monitors and continuous radon monitors. They keep a running record of radon levels over a specified period of time and can determine abnormal fluctuations in radon levels.

Alpha track and electrets ion chamber detectors are commonly used for long-term testing of 90 days or more. Long-term tests provide a year-round average of a home’s radon level. Short-term tests, including alpha track detectors, charcoal canisters, charcoal liquid scintillation detectors and electret ion chambers, range from two to 90 days and are the quickest way to find out if a home has elevated radon levels. Short-term tests are recommended for home owners who are selling their home. However, when doing a short-term test, a second test is recommended if the results indicate radon levels higher than 4 pCi/L.

Who Does the Testing?

Homeowners can buy radon test kits from qualified test providers or labs. Homeowners who elect to do the test on their own should not test during severe storms or wind; make sure windows and outside doors are closed for at least 12 hours before the start of the test and keep them closed throughout the test; place the testing device somewhere it will not be disturbed, at least 20 inches from the ground and away from high heat or humidity, drafts or exterior walls; and return the testing device immediately to the lab. Self-tests range from $10 to more than $100.

Another option for homeowners is to hire a professional radon tester. A professional tester can ensure optimal testing conditions, report and explain the results and, if the test shows high radon levels, provide guidance on fixing the radon problem. Often, home inspectors are qualified radon testers and can include a radon test as part of a routine home inspection. Prices run anywhere from around $50 to over $300.

The EPA recommends that homeowners test their home for radon before putting their home on the market. Homebuyers should confirm that a home has had favorable test results. If a radon test has not been done recently, the buyer should include it as part of the home inspection. Also, homeowners who are considering renovations in an unfinished area of the home should do a radon test both before starting the project so that high radon levels can be corrected as part of the renovation process. A second test should be done after the renovations have been completed to ensure the renovations have not affected radon levels.

Interested in finding a radon test? Take a look at our Radon Test Directory.

To learn more about radon, take a look at our interviews with three radon test experts, Elliott Wall, Stephen Gladstone and David Scott.