What Is Radon Testing?

How Can You Tell if Your Home is Safe From Radon?

How can you test your home for radon - the second leading cause of lung cancer?. istockphoto.com

Radon testing, a measurement done to detect the presence of radon gas in our homes, could theoretically prevent 20,000 deaths from lung cancer each year in the United States.

Radon gas is an invisible, odorless gas that is produced by the normal breakdown of uranium in the soil. Although some regions of the U.S. have higher levels of radon, elevated levels have been found in homes in all 50 states, and around the world.

At the present time, it is estimated that 1 out of 15 homes in the United States have elevated radon levels.

Thankfully, if elevated radon levels are detected and repaired, this cause of lung cancer is entirely preventable. Radon testing is easy, inexpensive, and doesn’t even require willpower.

Who Should Test

Since radon is an odorless, colorless gas, the only way to know if levels are abnormal in your home is through testing. The EPA recommends that every home in the United States be tested for radon. In the past, some people thought that homes without basements were not at risk, but this is not the case. Any living area below the 3rd floor of a building should be tested.

What Do the Results Mean?

Radon is present in small amounts in the air throughout the world. The average level of radon in outdoor air is 0.4 pCi/L (pico Curies per Liter), 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.

Importance of Testing in Lung Cancer Prevention

Exposure to radon in our homes is the 2nd leading cause of lung cancer and the number one cause in non-smokers.

To put the risk of radon in perspective, the EPA has a chart in which they compare the risk of radon to other risks. At a level of 4 pCi/L, the risk that non-smokers will develop lung cancer is about the same as the risk of dying in a car crash. For smokers, exposure to radon is of even greater concern. At a radon level of 4 pCi/L, the risk of developing lung cancer is 5 times the risk of dying in a car crash.

Methods of Radon Testing

Both short-term and long-term tests are available to test for radon.

Short-term tests
Short-term tests are the fastest way to detect elevated radon levels in your home and are performed over a period of 2 to 90 days (most test kits are done over 2 to 4 days). Do-it-yourself short-term kits are available at most hardware stores, and can also be ordered online or by phone (see below).

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

These tests can give an indication of what the average level of radon is in your home year round.


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 usually used by a certified radon testing company rather than as a do-it-yourself test and are usually more expensive.

How to Test for Radon

Carefully read and follow the manufacturer’s directions on your radon test kit. Some of these are very specific – for example, if your test is left out for more than the required amount of time, improperly sealed, or there is a delay between the test time and when you mail the test, your sample may be rejected. Most test kits recommend the following:

  • 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 (short-term tests)
  • 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

What Do I Do if Radon Testing Reveals Abnormal Levels in My Home?

If your radon level is above 4 pCi/L, the first step it to repeat the test. If the average of the tests remains above 4 pCi/L, it is recommended that you contact a professional to perform radon mitigation (see resources below).


Most hardware stores carry short-term radon test kits. Discounted kits are often available (especially during Radon Awareness Month in January) through state or county health departments. If you are interested in a qualified tester for radon, check with your state radon contract information. By phone, discounted test kits can be purchased at 1-800-SOS-RADON.

Radon Mitigation – Finding a Certified Professional

If your radon levels are elevated, it important to have your home repaired to reduce your families risk of lung cancer. Your state radon contact can provide you with a list of certified radon mitigation experts in your area.

Special Situations

In addition to entering your home through the soil, radon may be present in well water, or in items that we introduce into our homes such as granite countertops. If you are concerned about the possibility of radon in your water, check with your state radon contact. General information about radon in drinking water is available through the EPA’s Safe Drinking Water Hotline at 1-800-426-4791.​.

Further Reading:


Environmental Protection Agency. Radon. Updated 05/17/16. https://www.epa.gov/radon

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