Radon

Radon is a naturally occurring gas that can have a big impact on indoor air quality and your health.

You can't see or smell radon, and it can build up inside homes, buildings and schools to dangerous levels. Exposure to high levels of radon can cause lung cancer. Learn about radon, how it affects lung health and what you can do about it.

Radon Facts

Radon is a colorless, tasteless and odorless gas that causes lung cancer. Exposure to radon is the second leading cause of lung cancer in the United States, after smoking. Radon-related lung cancers result in an estimated 21,000 deaths annually in the United States.

Radon forms naturally. Uranium in soil or rock breaks down to form radium, which then turns into radon gas. Once formed, radon enters a building through cracks in walls, basement floors, foundations and other openings. As radon decays, it releases radioactive byproducts that are inhaled and can cause lung cancer. Because radon comes from rock and soil, it can be found anywhere. Being exposed to limited amounts, like those found outdoors, is impossible to avoid. However, when radon gets trapped indoors, it may exist in dangerous at dangerous amounts.

Less often, radon may enter buildings from water used in bathroom showers and faucets. Concerns have also been raised about the radon released indoors from building materials, such as granite counter tops or tiles. However, these sources have rarely proven to be a problem.

Radon is the second leading cause of lung cancer in the United States, responsible for thousands of deaths each year. Exposure to radon causes no immediate symptoms, but the long-term threat of lung cancer is important to everyone. People who have never smoked make up one out of 7 radon-related lung cancer deaths each year.

The health hazard comes from radioactive particles released when radon decays. These particles can be inhaled into the lung and attack your cells with dangerous, cancer-causing radiation. Smoking and radon exposure can separately increase the risk of lung cancer. But if you smoke, know that exposure to both greatly enhances the risk of lung cancer.

Every home should be tested for radon. Radon has been found in high amounts in homes in every state. Your home can have elevated levels of radon while your neighbor's home does not. Testing is the only way to know if radon is a problem in your home. Radon testing is easy and low cost, and it could save your life. Thousands of lung cancer deaths could be avoided each year if home and building owners acted to test and fix.

The only way to detect a buildup of radon in your home is to test the air. Do-it-yourself test kits and digital detectors are simple to use and low in cost.

Short-term tests usually take two to seven days. To use a short-term radon test, place the kit in the lowest level regularly used in your home and where it will not be disturbed. Follow the test directions and other guidance to prevent problems that can affect the testing. Once the testing period is complete, seal the test kit and send it to a laboratory for analysis. Most test kits include the cost of lab analysis. In a matter of weeks, you will be told of the radon level in your home.

Long-term tests tend to be more accurate because they collect more data. Long-term radon tests take at least three months and measure long-term averages. If you do not want to wait for a long-term test, short-term tests can tell if your home has a problem and requires follow-up testing. Order a radon test kit today.

Digital detectors can be purchased for your home and can provide short-term readings and report an average for the long term.

If you prefer, hire a certified radon-testing professional. The best way to find a certified professional is to contact your state radon program.

Radon gas is measured in picocuries per liter (pCi/L) of air. The EPA recommends taking action to reduce radon if the result is 4.0 pCi/L or greater and to consider similar actions when the radon level is between 2 and 4.0 pCi/L. The goal is to get your radon level to the lowest level possible.

There are several ways to protect you and your family from the dangers of radon gas.

 

If you have an existing home with elevated levels of radon, you can fix the problem by having a radon mitigation system installed by a certified radon professional. A radon mitigation system typically consists of:

  • Sealing cracks in the foundation, floors, walls, piping or other areas that are allowing radon to enter.
  • Installing a vent pipe that draws radon from soil underneath the foundation and vents it outdoors – this is called a passive mitigation system. 
  • If extra power is needed, an exhaust fan can be connected to the vent pipe for extra power to draw radon from the soil – this is called an active mitigation system. 

The type and cost of a mitigation system depends on the size of the home, house design, foundation type and other characteristics. The cost can range from $1,00 - $2,500 or more. Installing a mitigation system is an investment in your home and your health. It is always recommended to re-test your home within 24 hours – 30 days after a mitigation system is installed and every 2 years after that. Find certified radon mitigation professionals by contacting your state radon program.

If you are building a new home, ask your contractor to install radon-resistant features. These features include gravel and plastic sheeting below the foundation, sealing of cracks and the installation of a vent pipe. Once the radon-resistant features have been installed and the home is completely built, make sure to perform a radon test, as the levels could still be elevated. If the radon levels are still elevated, a radon fan should be added to the system to lower the radon level.

Detailed information about radon reduction in your home or building can be found in EPA's Consumer's Guide to Radon Reduction.

The American Lung Association is working with national partners and government agencies to build in ways to reduce radon in all homes. The National Radon Action Plan outlines strategies to protect millions more people from dangerous radon exposure.

Radon and Lung Health

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Radon is a naturally occurring, radioactive gas that you can’t see, smell or taste. Radon is the second leading cause of lung cancer.

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Order a Radon Test Kit

Radon is a naturally occurring gas that can negatively impact your indoor air quality and your health. You can't see or smell it. Radon can build up inside your home to dangerous levels. Exposure to high levels of radon can cause lung cancer. The only way to know if your home has high levels of radon is to test. Testing is easy and inexpensive.
Order Your Test Kit Today

Conducting an At-Home Radon Test

If you are conducting an at-home radon test, there are steps you should take to make sure you receive accurate test results.

Place the detector(s) in the lowest area(s) suitable for occupancy and are frequently used, such as: 

  • a family room
  • living room
  • den
  • playroom
  • bedroom
  • exercise room

Do not measure in kitchens, laundry rooms or bathrooms (fan systems and humidity may affect detectors). Do not test in crawlspaces, on floor or wall cracks, or directly next to a sump pump, as this may cause a false high reading. 

Once you have chosen the room you will conduct your test, the test should be placed:

  • In areas where it will not be disturbed 
  • At least 3 feet from doors and windows to the outside 
  • At least 1 foot from exterior walls 
  • 20 inches to 6 feet from the floor 
  • At least 4 inches away from objects horizontally and directly above the detector 
  • Away from drafts 
  • Away from heat, fireplaces, furnaces, direct sunlight and areas of high humidity 

Make sure to read and follow all of the instructions that come with your test kit. Some other guidelines that your test kit will include are:

  • Be sure to maintain closed-house conditions. This means to keep all windows closed, keep doors closed except for normal entry and exit, and no operation of fans or other appliances which bring in outside air. Begin closed-house conditions at least 12 hours prior to the start of the testing period. 
  • Operate home heating and air conditioning normally during the test. For tests lasting less than one week, only operate air conditioning units that recirculate interior air. 
  • Do not conduct short-term tests during or immediately following severe storms or periods of high winds as these events can temporarily increase radon levels.

Radon Tools and Resources

Healthcare Professionals

The American Lung Association has developed a variety of tools to aid healthcare professionals in identifying, screening, and treating patients at-risk for the health impacts of radon. Our new toolkit provides a selection of videos, factsheets, decision support tools, and patient education tools.
Healthcare Toolkit

Home Buyers and Real Estate Professionals

Home buyers and real estate professionals alike play an important role in ensuring homes are safe and healthy. The American Lung Association has resources to help both groups understand the risks of radon and take steps to protect against it during the home buying process.

Home Buyers Toolkit

Real Estate Resources

Advocates and Decision Makers

Policy decision makers and advocates are essential in protecting public health by supporting measures that reduce exposure to harmful pollutants like radon. These resources can help inform policy efforts, promote radon testing and mitigation, and advance strategies that ensure healthier homes and communities.
Advocate Resources

Schools

Radon is a serious health risk that can affect anyone—including children and staff in school buildings. To support schools in creating healthier learning environments, the American Lung Association offers resources with practical guidance on radon testing, mitigation, and education.
School resources

Find Out Radon Initiatives in Your Community

Radon in Illinois

Radon Action Month

January is National Radon Action Month and the American Lung Association urges everyone to help save lives by testing their home for radon and mitigate if high levels are detected.

Page last updated: June 23, 2025

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