Radon in the Home

What is Radon?

Radon is a gas that you cannot smell, taste or see. Radon forms naturally when uranium, thorium, or radium, (radioactive metals) breaks down in rocks, soil and groundwater. People can be exposed to radon primarily from breathing radon in air that comes through cracks and gaps in buildings and homes. Because radon comes naturally from the earth, people are always exposed to it.

  • Having your home tested is the only effective way to determine whether you or your family is at risk of high radon exposure.
  • For more information on testing your home, check with your state radon officeexternal icon  or call the National Radon Hotline at 1-800-SOS-RADON.


National Radon Action Plan released on November 9, 2015
Image of National Radon Action Plan front cover

The National Radon Action Plan: A Strategy for Saving Lives sets out strategies to drive the changes needed to reduce exposure to radon, a naturally occurring, invisible and odorless gas. This plan was released by the American Lung Association on November 9, 2015.

Read the National Radon Action Plan on the American Lung Association’s website here pdf icon[PDF – 782kb]external icon


Radon Communication Toolkit

For more information about radon, visit CDC’s new web page Protect Yourself and Your Family from Radon which brings together radon information from across the agency. CDC’s Radon Communication Toolkit, which is also featured on the new radon web page is designed for environmental and public health professionals to use to increase awareness and understanding of radon, its health effects, and the importance of testing for radon among the communities they serve. The toolkit contains customizable fact sheets, infographics, newsletter articles, and social media posts.

Illustration of how radon can get into your home.

The EPA lists the following ways that radon can get into buildings:

  • Cracks in solid floors and walls (#1 and #3 in the figure)
  • Construction joints (#2)
  • Gaps in suspended floors (#4)
  • Gaps around service pipes (#5)
  • Cavities inside walls (#6)
  • The water supply (#7)

For information on reducing radon levels in your home, please see the EPA page “Basic Radon Facts”.external icon

Radon in Soil

Radon gets into the indoor air primarily through pores and cracks in the soil under homes and other buildings.  Usually, the air pressure in homes and buildings is lower than the pressure outside in the soil around or underneath the foundation.  The pressure difference will create suction.  Radon will come through cracks due to that suction (even at low levels). For more information about the risks from radon in homes, please see EPA’s Assessment of Risks from Radon in Homes. pdf icon[PDF]external icon

Radon in Water

Radon gas can be present in water that comes into your home.  Radon is not a concern if the source of the water is from lakes, rivers, and reservoirs.  In those cases, the radon is mostly released into the air before it enters your home.  There may be a concern when your home’s water supply is from underground sources (groundwater), such as wells.  For those instances radon can escape from the water during everyday activities such as drinking, washing dishes, cooking and showering.  These actions could make a small contribution to the radon gas present in the air in your home.

Illustration of radon entering the nose and mouth.

When you breathe in radon, radioactive particles from radon gas can get trapped in your lungs. Over time, these radioactive particles increase the risk of lung cancer. It may take years before health problems appear.

Radon is the second leading cause of lung cancer after cigarette smoking. The U.S. Environmental Protection Agency and the Surgeon General’s office estimate radon is responsible for more than 20,000 lung cancer deaths each year in the U.S.


Smoking and Radon

Man Smoking a Cigarette

People who smoke and are exposed to radon are at a greater risk of developing lung cancer.  EPA recommends taking action to reduce radon in homes that have a radon level at or above 4 picocuries per liter (pCi/L) of air (a “picocurie” is a common unit for measuring the amount of radioactivity).

The chances of getting lung cancer are higher if your home has elevated radon levels and you smoke or burn fuels that increase indoor particles.  For more information, please see Health Risks of Radonexternal icon.

Your chances of getting lung cancer from radon depend mostly on:

  • How much radon is in your home–the location where you spend most of your time (e.g., the main living and sleeping areas).
  • The amount of time you spend in your home
  • Whether you are a smoker or have ever smoked
  • Whether you burn wood, coal, or other substances that add particles to the indoor air


For more information on cigarette smoking and radiation, click here

Having your home tested is the only effective way to determine whether you and your family are exposed to high levels of radon. The U.S. Surgeon General recommends ALL homes be tested for radon gas.

Steps you can take to measure and reduce radon levels include:

  • Purchasing a radon test kit
  • Testing your home or office
  • Testing is inexpensive and easy — it should only take a few minutes of your time. It requires opening a package and placing a small measuring device in a room and leaving it there for the desired period. Short-term testing can take from a few days to 90 days.  Long-term testing takes more than 90 days.  The longer the test, the more relevant the results are to your home and lifestyle.
  • Sending the kit to appropriate sources to determine radon level
    • Follow the directions on the test kit packaging to find out where to send the device to get the results.
  • Fixing your home if radon levels are high


CDC worked with EPA to produce the booklet A Citizen’s Guide to Radon: The Guide to Protecting Yourself and Family from Radon pdf icon[PDF – 713kb]external icon. Over the years, federal, state, and local agencies have used this citizen’s guide to alert and to inform people about residential radon risks.

Image of EPA publication A Citizens Guide to Radon

The publication includes information about the following:

  • The Risks of Living with Radon
  • Lowering Radon Levels in Your Home
  • How to Test Your Home for Radon
  • What your Test Results Mean
  • Radon Myths


How a Radon Test Kit Works

When selecting a radon test kit, EPA recommends that you contact your state radon officeexternal icon for help in finding the radon kit that would work best for your home. You can measure radon levels in your home in two ways: short-term testing and long-term testing.

  • Short-term radon test kits  stay in your home for 2 to 90 days. A short-term test will give you quicker results, but it won’t tell you what your radon levels are throughout the year because radon levels change over the course of the day, with seasons, and with weather changes. Experts recommend testing your home at least two different times to get a better idea of how much radon is in your home.
  • Long-term radon test kits  stay in your home longer than 90 days. These will give you a better idea of what your radon levels are year-round.

Please contact the EPA hotline at 1 800 767-7236 for more information on short and long term test kits and how you can obtain a kit.

EPA recommends taking action to reduce radon in homes that have a radon level at or above 4 picocuries per liter (pCi/L) of air.

Radon is measured in picocuries per liter of air (pCi/L). The lower the average pCi/L level in the air you breathe, the lower your risk of getting lung cancer.  The chart below provides more information.

Radon Risk
If your radon level is Take action
Higher than 4 pCi/L Take a second test to make sure the first test results were accurate. You can use another short-term test, or you can buy a long-term test.
Contact a licensed professional to install a radon reduction system if:
• The average of both short-term tests is higher than 4 pCi/L
• Results from a long-term test are also higher than 4 pCi/L
Between 2 pCi/L and 4 pCi/L Consider installing a radon reduction system.
If you do this, test for radon again in a few months to see how effective the system is for reducing radon levels.
Lower than 2 pCi/L No action needed. Test your home again if you start living on a lower level (for example, if you turn your basement into a home office or extra bedroom).

To find out more about radon test kits, contact the EPA Radon Hotlines and Information Resourcesexternal icon or refer to the EPA radon web siteexternal icon on how to use a test kit.

The U.S. Department of Housing and Urban Developmentexternal icon recommends additional actions you can take to reduce high radon levels in your home and protect yourself from an increased risk of lung cancer.

  • Stop smoking and discourage smoking in your home.
    • Smoking significantly increases the risk of lung cancer from radon.
  • Increase air flow in your house by opening windows and using fans and vents to circulate air.
    • Natural ventilation in any type of house is only a temporary strategy to reduce radon.
  • Seal cracks in floors and walls with plaster, caulk, or other mate­rials designed for this purpose.
    • Contact your state radon office for a list of qualified contractors in your area and for information on how to fix radon problems yourself. Always test again after finishing to make sure you’ve fixed your radon problem.
  • Ask about radon resistant construction techniques if you are buying a new home.
    • It is almost always cheaper and easier to build these features into new homes than to add them later.
Related Links

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For more information, go to the EPA webpageexternal icon

Radon in the Home

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Page last reviewed: January 30, 2020