Learn About Radon Testing

Radon testing is performed to detect the presence of radon gas in homes. As the second leading cause of lung cancer and a potential risk factor for leukemia and lymphoma, radon is an odorless, colorless gas that can only be detected by testing. If levels are abnormal, radon mitigation (a process to reduce gas concentrations or radon in water) can almost always solve the problem and eliminate your risk.

Testing Recommendations

Radon gas is produced by the normal breakdown of uranium in the soil. Although some regions of the United States have higher levels of radon, elevated levels have been found in homes in all 50 states and around the world. It is estimated that no less than one out of 15 American homes has elevated radon levels.

The Environmental Protection Agency (EPA) currently recommends testing all homes for radon below the third floor as well as all schools.

In addition to soil, radon may be present in well water or items that we introduce into our homes (such as granite countertops). Since radon has no smell and is essentially invisible, the only way to know you have a problem is through testing. Testing is inexpensive and should only take a few minutes to perform.

Normal and Abnormal Levels

Radon is present in small amounts in the air throughout the world. The average level of radon in outdoor air is 0.4 picoCuries per liters (pCi/L), and the average level in indoor air is 1.3 pCi/L.

The EPA recommends fixing your home if the radon level is above 4 pCi/L. They also state that individuals should consider repairs if the level falls between 2 pCi/L and 4 pCi/L

It should be noted that home with borderline radon levels may still benefit from mitigation if you are a smoker or live in a house with smokers. The presence of radon at 2 pCi/L can amplify the health risks of tobacco smoking, still the number one risk factor for lung cancer overall.

Radon and Lung Cancer

Exposure to radon in homes is not only the second leading cause of lung cancer overall but the number one cause in non-smokers.

According to the EPA, the prevalence of lung cancer among non-smokers increases in tandem with the concentration of radon detected in a home:

  • At 2 pCi/L, approximately 4 out of 1,000 people will get lung cancer.
  • At 4 pCi/L, approximately 7 out of 1,000 people will get lung cancer.
  • At 8 pCi/L, approximately 15 out of 1,000 people will get lung cancer.
  • At 10 pCi/L, approximately 18 out of 1,000 people will get lung cancer.
  • At 20 pCi/L, approximately 36 out of 1,000 people will get lung cancer.

If you are a smoker, the prevalence skyrockets:

  • At 2 pCi/L, approximately 32 out of 1,000 people will get lung cancer.
  • At 4 pCi/L, approximately 64 out of 1,000 people will get lung cancer.
  • At 8 pCi/L, approximately 120 out of 1,000 people will get lung cancer.
  • At 10 pCi/L, approximately 150 out of 1,000 people will get lung cancer.
  • At 20 pCi/L, approximately 260 out of 1,000 people will get lung cancer.

Radon and Blood Cancers

A 2016 study in the journal Environmental Research suggests that indoor radon exposure may also increase the risk of blood cancers such as leukemia, lymphomas, and multiple myeloma in women, with the risk increasing in tandem with rising radon levels.

A 2017 study in Environmental Research and Public Health estimates that every 10 Bq/m3 (roughly one-third of 1 pCi/L) increase in radon is associated with a 7% increase in the risk of lymphoma in women, children, and adolescents.

The reasons for this are not entirely clear, but scientists do know that radon emits alpha particles that can damage DNA in the bone marrow and potentially contribute to the development of blood cancers.

Radon Testing Methods

There are both short-term and long-term tests available to test for radon. Short-term tests are good if you want an instant reading of the status of your home. They are also important as part of home inspections when buying or selling houses. Long-term tests are used to monitor radon levels over a period of time, as they can be low in some seasons and high in others.

Short-Term Tests

Short-term tests are the fastest way to detect elevated radon levels in your home. They are performed over a period of two to 90 days, with most retail kits designed for 2- to 4-day testing.

Do-it-yourself kits are available at most hardware stores and can also be ordered online. Many home inspection agencies offer radon detection as part of the inspection service.

Long-Term Tests

Long-term tests are conducted over a period of more than 90 days. Radon levels fluctuate throughout the year and are highest during cold weather when heating is used and windows are shut.

These tests can give an indication of the average level of radon is in your home year-round. Most often, long-term tests are used by those who have done radon mitigation and want to make sure that the interventions are working.

Types of Devices

Both passive and active devices can be used for radon testing. Passive devices, such as charcoal canisters, do not require power and are widely available.

Active devices require power to run and can provide continuous monitoring of radon levels. These devices are expensive and typically used by a certified radon testing company rather than as a do-it-yourself test.


Most hardware stores carry short-term radon test kits that cost less than $20. Free or discounted kits are often available through state or county health departments (especially during Radon Awareness Month in January). Discounted tests can be purchased from the National Radon Hotline at 1-800-SOS-RADON.

General information about radon in drinking water is available through the EPA’s Safe Drinking Water Hotline at 1-800-426-4791.

How to Test for Radon

Carefully read and follow the manufacturer’s directions on your radon test kit. Some of the tests are very specific and may deliver tainted results if the timing is not correct or the test is not mailed back to the manufacturer's lab within the allotted timeframe.

Most home radon tests have similar instructions:

  • Place the test kit in the lowest area of living space in your home.
  • Keep windows and doors closed (except for entering and leaving) for 12 hours prior to testing your home and throughout the duration of the test.
  • Avoid placing the test kit in the kitchen, bathrooms, hallways, laundry room, and rooms that may be drafty.
  • Place the kit at least 20 inches off the floor

If your radon level is above 4 pCi/L, always be sure to repeat the test to confirm the results. If the average of the results remains above 4 pCi/L, it is strongly recommended that you contact a professional to perform radon mitigation.

Radon Mitigation

If your radon levels are elevated, it important to find qualified radon tester in your area. You can do so by using the online locator offered by the National Radon Safety Board (NRSB) or by contacting your state radon or public health office.

Radon mitigation in the air is accomplished through ventilation, often by drilling holes in the floor slab of the house and suctioning gas under pressure from the underlying soil. Above-slab mitigation requires sealing the house in an airtight envelope and suctioning gas out of ventilation systems, wall spaces, and crawlspaces.

Radon mitigation in water involves activated charcoal filter systems. There are also water aeration systems that can release radon into the air from open wells as a pollutant.

A Word From Verywell

Testing for radon is one of the least expensive ways to reduce your risk of lung cancer, whether you smoke or not. If you do smoke, be aware that the combination of radon and tobacco smoke not only puts you at risk of cancer but also anyone you live with.

Even if radon testing shows no signs of the gas, smoking cessation is something ever smoker should consider if living with children or loved ones. Nonsmokers exposed to secondhand smoke increase their risk of lung cancer by anywhere from 20% and 30%. 

Many smoking cessation aids are classified as Essential Health Benefits (EHBs) under the Affordable Care Act and may be available free of charge even for multiple quit attempts.

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Article Sources
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