How to Test for Radon

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Active radon gas testing gives you a continuous reading of radon levels over the testing period.
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Long-term exposure to elevated levels of radon gas in homes and in certain kinds of workplaces, such as mines, is a leading cause of lung cancer. The U.S. Surgeon General and the Environmental Protection Agency estimate that about 21,000 lung cancer deaths per year are attributable to radon exposure. Smokers are particularly susceptible to the effects of radon and account for approximately 18,100 of those radon-induced deaths.


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The effects of radon are cumulative and result from long-term exposure. The potential of a radon problem in your home need not be a cause for panic. Test to assess your home's radon levels and, if radon is present, address the problem through established, appropriate mitigation procedures. State and local radon offices can advise you on where to start.


What Is Radon?

Radon is a radioactive gas, the product of the radioactive decay of natural uranium in rock, soil, and sometimes water. It's odorless and colorless, so you can't detect it without a test. The radon gets into your home by infiltrating cracks in your foundation and through unsealed gaps around pipes and structure.


Because radon atoms resist forming larger compound molecules, they are small and able to penetrate the molecular structure of many common building materials such as concrete and gypsum wallboard. Radon gas atoms are comparatively heavy—nine times heavier than ordinary air—so they tend to concentrate in the lowest parts of your home, typically a basement or crawl space. When you test for radon, the tests should be conducted in the lowest livable space.


Radon Testing Equipment

Devices for detecting the presence and levels of radon gas can be divided into two basic groups: passive testing units and active ones. Passive testing is a procedure that homeowners can easily conduct themselves. The devices for passive testing are readily available from home improvement retailers or from online sources, and some municipalities even offer free passive radon gas test kits to their citizens.


Passive Radon Testing

Passive radon gas testing devices come in two subgroups—short term detectors and long term detectors. A short-term passive detector usually takes the form of charcoal canisters while long-term tests are generally alpha track detectors.

The standard procedure for passive radon testing is to place the collection unit as directed and leave it undisturbed for the length of time specified. For short term units, that period may be up to seven days. Long term radon detectors will stay in place from 90 days to a year. The collection device must then be sent to a laboratory for analysis.


Performing the Tests

Your passive test kit will come with full instructions. The idea is to test in a low-level room that is used regularly. Several factors can affect radon test results, including the test location, weather and drafts, so following the directions is important for accuracy.


Keep doors and windows closed except for necessary entry and exit. The test can be skewed by excessive humidity, so it's best to keep outside doors and windows closed for 12 hours preceding the test and to avoid testing when the humidity is high. Place the detector at least 20 inches above the floor.

Readings from passive radon tests, especially the short term ones, will be approximate. They're most useful as a means to indicate whether or not you have a radon problem in your home. If the passive test shows the presence of radon at significant levels, it is recommended that you have an active radon test conducted.


Active Radon Testing

Active radon gas testing devices are much more sophisticated—and accurate—than passive ones and are typically deployed by home inspectors or by air quality professionals. Active radon tests measure and record radon levels throughout the duration of the test. If radon levels rise or fall during the day, those variations will be shown. The active test will provide you with a certified report of your home's radon condition.

Interpreting the Radon Test Results

Radon is measured in terms of picocuries per liter, abbreviated as pCi/L. Certain low levels of radon gas are commonly present and normal—about 0.4 pCi/L outside and, on average, about 1.3 pCi/L indoors. If testing shows the level of radon in your home is at 4 pCi/L or higher, the Environmental Protection Agency recommends that you employ radon mitigation techniques to bring those levels down. Mitigation techniques include taking steps to seal obvious easy entry points for radon and a system that will reduce the radon gas levels inside.

Keeping Your Home Safe

A relatively new generation of radon detection devices aimed at the homeowner has come on the market. Like smoke detectors and carbon monoxide monitors, these new devices are affixed permanently in your home and provide a continuous reading of radon gas levels. Some of them can be accessed remotely from your smartphone. Like the professional testing equipment, these devices provide a radon-level reading in real time and may offer you reassurance post-testing and post-mitigation.

Radon contamination can be a serious problem, but it need not be. Passive preliminary radon test kits are widely available and are inexpensive or free. You can conduct passive tests yourself. Radon mitigation, where needed, employs a variety of strategies, including a radon mitigation system and sealing your lowest level. A radon mitigation contractor can recommend the one most suited to your home, the one that will best address the particulars of its radon infiltration.