Radon Facts

“Home Buyer’s and Seller’s Guide to Radon”

EPA 402/K-09/002, January 2009

  1. Why Should I Test for Radon?a. Radon Has Been Found in Homes All Over the United States
    b. EPA and the Surgeon General Recommend That You Test Your Home
  2. I’m Selling a Home. What Should I Do?a. If Your Home Has Already Been Tested for Radon
    b. If Your Home HasNot Yet Been Tested for Radon
  3. I’m Buying a Home. What Should I Do?a. If the Home Has Already Been Tested for Radon
    b. If the Home HasNot Yet Been Tested for Radon
  4. I’m Buying or Building a New Home. How Can I Protect My Family?a. Why Should I Buy a Radon-Resistant Home?
    b. What Are Radon-Resistant Features?
  5. How Can I Get Reliable Radon Test Results?a. Types of Radon Devices
    b. General Information for All Devices
    c. Preventing or Detecting Test Interference
    d. Length of Time to Test
    e. Doing a Short-Term Test
    f. Using Testing Devices Properly for Reliable Results
    g. Interpreting Radon Test Results
    Radon and Smoking
    Radon Testing Checklist
  1. What Should I Do If the Radon Level is High?a. High Radon Levels Can Be Reduced
    b. How to Lower the Radon Level in Your Home
    c. Selecting a Radon-Reduction (Mitigation) Contractor
    d. What Can a Qualified Radon-Reduction Contractor Do for You
    e. Radon in Water
  2. Radon Myths and Facts
  3. Need More Information About Radon?a. Web sites (EPA)
    b. Radon Hotlines (Toll-Free)
    c. Printed Documents
    Radon Risk and Testing
    Reducing Radon Levels in a Home
    Building a New Home to Be Radon-Resistant
    Radon Technical Guidance
  4. State Radon Offices
  5. EPA Regional Offices

PDF Version (PDF, 44 pp, 4MB)

En Español – La Versión en formata PDF (en formata PDF, 52 páginas, 604KB acerca de en formata PDF)


EPA Recommends:

  • If you are buying a home or selling your home, have it tested for radon.
  • For a new home, ask if radon-resistant construction features were used and if the home has been tested.
  • Fix the home if the radon level is 4 picocuries per liter (pCi/L) or higher.
  • Radon levels less than 4 pCi/L still pose a risk, and in many cases, may be reduced.
  • Take steps to prevent device interference when conducting a radon test.
EPA estimates
that radon
of cancer
deaths in
the U.S.
each year.
radon health risks
* Radon is estimated to cause about 21,000 lung cancer deaths per year, according toEPA’s 2003 Assessment of Risks from Radon in Homes (EPA 402-R-03-003). The numbers of deaths from other causes are taken from the Centers for Disease Control and Prevention’s 2005-2006 National Center for Injury Prevention and Control Report and 2006 National Safety Council Reports.


EPA Risk Assessment for Radon in Indoor Air

EPA has updated its estimate of the lung cancer risks from exposure to radon in indoor air. The Agency’s updated risk assessment, “EPA Assessment of Risks from Radon in Homes” [EPA 402-R-3-003]. EPA’s assessment was based on the National Academy of Sciences’ (NAS) report on the “Health Effects of Exposure to Radon” (BEIR VI, 1999). The Agency now estimates that there are about 21,000 annual radon-related lung cancer deaths, an estimate consistent with the NAS Report’s findings.

This Guide answers important questions about radon and lung cancer risk. It also answers questions about testing and fixing for anyone buying or selling a home.

Radon Is a Cancer-Causing, Radioactive Gas

You cannot see, smell, or taste radon. But it still may be a problem in your home. When you breathe air containing radon, you increase your risk of getting lung cancer. In fact, the Surgeon General of the United States has warned that radon is the second leading cause of lung cancer in the United States today. If you smoke and your home has high radon levels, your risk of lung cancer is especially high.

You Should Test for Radon

Testing is the only way to find out your home’s radon levels. EPA and the Surgeon General recommend testing all homes below the third floor for radon.


You Can Fix a Radon Problem

If you find that you have high radon levels, there are ways to fix a radon problem. Even very high levels can be reduced to acceptable levels.


If You Are Selling a Home…

EPA recommends that you test your home before putting it on the market and, if necessary, lower your radon levels. Save the test results and all information you have about steps that were taken to fix any problems. This could be a positive selling point.


If You Are Buying a Home…

EPA recommends that you know what the indoor radon level is in any home you consider buying. Ask the seller for their radon test results. If the home has a radon-reduction system, ask the seller for information they have about the system.

If the home has not yet been tested, you should have the housed tested.

If you are having a new home built, there are features that can be incorporated into your home during construction to reduce radon levels.

The radon testing guidelines in this Guide have been developed specifically to deal with the time-sensitive nature of home purchases and sales, and the potential for radon device interference. These guidelines are slightly different from the guidelines in other EPA publications which provide radon testing and reduction information fornon-real estate situations.

This Guide recommends three short-term testing options for real estate transactions. EPA also recommends testing a home in the lowest level which is suitable for occupancy, since a buyer may choose to live in a lower area of the home than that used by the seller.


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1. Why Do You Need to Test for Radon?

a. Radon Has Been Found In Homes All Over the U.S.

Radon is a radioactive gas that has been found in homes all over the United States. It comes from the natural breakdown of uranium in soil, rock and water and gets into the air you breathe. Radon typically moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Radon can also enter your home through well water. Your home can trap radon inside.

Any home can have a radon problem. This means new and old homes, well-sealed and drafty homes, and homes with or without basements. In fact, you and your family are most likely to get your greatest radiation exposure at home. That is where you spend most of your time.

Nearly 1 out of every 15 homes in the United States is estimated to have an elevated radon level (4 pCi/L or more). Elevated levels of radon gas have been found in homes in your state. Contact yourstate radon office for information about radon in your area.

b. EPA and the Surgeon General Recommend That You Test Your Home

Testing is the only way to know if you and your family are at risk from radon. EPA and the Surgeon General recommend testing all homes below the third floor for radon.


You cannot predict radon levels based on state, local, and neighborhood radon measurements. Do not rely on radon test results taken in other homes in the neighborhood to estimate the radon level in your home. Homes which are next to each other can have different radon levels. Testing is the only way to find out what your home’s radon level is.

In some areas, companies may offer different types of radon service agreements. Some agreements let you pay a one-time fee that covers both testing and radon mitigation, if needed. Contact your state radon office to find out if these are available in your state.

U.S. Surgeon General Health Advisory

“Indoor radon gas is the second-leading cause of lung cancer in the United States and breathing it over prolonged periods can present a significant health risk to families all over the country. It’s important to know that this threat is completely preventable. Radon can be detected with a simple test and fixed through well-established venting techniques.” January 2005

2. I’m Selling a Home. What Should I Do?

a. If Your Home Has Already Been Tested for Radon…

If you are thinking of selling your home and you have already tested your home for radon, review the Radon Testing Checklist to make sure that the test was done correctly. If so, provide your test results to the buyer.

No matter what kind of test you took, a potential buyer may ask for a new test especially if:

  • The Radon Testing Checklist items were not met;
  • The last test is not recent, e.g., within two years;
  • You have renovated or altered your home since you tested; or
  • The buyer plans to live in a lower level of the house than was tested, such as a basement suitable for occupancy but not currently lived in.

A buyer may also ask for a new test if your state or local government requires disclosure of radon information to buyers.

b. If Your Home Has Not Yet Been Tested for Radon…

Have a test taken as soon as possible. If you can, test your home before putting it on the market. You should test in the lowest level of the home that could be used regularly. This means testing in the lowest level that you currently live in or a lower level not currently used, but which a buyer might use as a family room or play area, etc.

The radon test result is important information about your home’s radon level. Some states require radon measurement testers to follow a specific testing protocol. If you do the test yourself, you should carefully follow the testing protocol for your area or EPA’s Radon Testing Checklist. If you hire a contractor to test your residence, protect yourself by hiring a qualified individual or company.

You can determine a service provider’s qualifications to perform radon measurements or to mitigate your home in several ways. Check with your state radon office. Many states require radon professionals to be licensed, certified, or registered. Most states can provide you with a list of knowledgeable radon service providers doing business in the state. In states that don’t regulate radon services, ask the contractor if they hold a professional proficiency or certification credential.Such programs usually provide members with a photo-ID card, which indicates their qualification and its expiration date. If in doubt, you should check with their credentialing organization. Alternatively,ask the contractor if they’ve successfully completed formal training appropriate for testing or mitigation, e.g., a course in radon measurement or radon mitigation.

A note on what qualified may mean

You should first call your state radon office for information on qualified radon service providers and state-specific radon measurement or mitigation requirements. SeeSection 9 for information on which states have certification, licensing, or registration programs. For up-to-date information on state radon program offices, click this link. EPA’s detailed and technical guidance on radon measurement and mitigation is included in Section 8; however, state requirements or guidance may be more stringent. For more information on the private sector radon credentialing programs, see www.epa.gov/radon/radontest.html

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3. I’m Buying a Home. What Should I Do?

a. If the Home Has Already Been Tested for Radon…

If you are thinking of buying a home, you may decide to accept an earlier test result from the seller or ask the seller for a new test to be conducted by a qualified radon tester. Before you accept the seller’s test, you should determine:

  • The results of previous testing;
  • Who conducted the previous test: the homeowner, a radon professional, or some other person;
  • Where in the home the previous test was taken, especially if you may plan to live in a lower level of the home. For example, the test may have been taken on the first floor. However, if you want to use the basement as living space, test there; and
  • What, if any, structural changes, alterations, or changes in the heating, ventilation, and air conditioning (HVAC) system have been made to the house since the test was done. Such changes may affect radon levels.

If you accept the seller’s test, make sure that the test followed the Radon Testing Checklist.

If you decide that a new test is needed, discuss it with the seller as soon as possible. If you decide to use a qualified radon tester, contact your state radon office to obtain a copy of their approved list of radon testing companies. See also www.epa.gov/radon/radontest.html

b. If the Home Has Not Yet Been Tested for Radon…

Make sure that a radon test is done as soon as possible. Consider including provisions in the contract specifying:

  • Where the test will be located;
  • Who should conduct the test;
  • What type of test to do;
  • When to do the test;
  • How the seller and the buyer will share the test results and test costs (if necessary); and
  • When radon mitigation measures will be taken and who will pay for them.

Make sure that the test is done in the lowest level of the home that could be used regularly. This means the lowest level that you are going to use as living space whether it is finished or unfinished.A state or local radon official or qualified radon tester can help you make some of these decisions.

If you decide to finish or renovate an unfinished area of the home in the future, a radon test should be taken before starting the project and after the project is finished. Generally, it is less expensive to install a radon-reduction system before (or during) renovations rather than afterwards.

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4. I’m Buying or Building a New Home. How Can I Protect My Family?

a. Why Should I Buy a Radon-Resistant Home?

Radon-resistant techniques work. When installed properly and completely, these simple and inexpensive passive techniques can help to reduce radon levels. In addition, installing them at the time of construction makes it easier to reduce radon levels further if the passive techniques don’t reduce radon levels below 4 pCi/L. Radon-resistant techniques may also help to lower moisture levels and those of other soil-gases. Radon-resistant techniques:







bullet Making Upgrading Easy: Even if built to be radon-resistant, every new home should be tested for radon as soon as possible after occupancy. If you have a test result of 4 pCi/L or more, a vent fan can easily be added to the passive system to make it an active system and further reduce radon levels.
bullet Are Cost-Effective: Building radon-resistant features into the house during construction is easier and cheaper than fixing a radon problem from scratch later. Let your builder know that radon-resistant features are easy to install using common building materials.
bullet Save Money: When installed properly and completely, radon-resistant techniques can also make your home more energy efficient and help you save on your energy costs.

Including passive radon-resistant features in a new home during construction usually costs less than fixing the home later. If you radon level is 4 pCi/L or more, consult a qualified mitigator to estimate the cost of upgrading to an active system by adding a vent fan to reduce the radon level. In an existing home, the cost to install a radon mitigation system is about the same as for other common home repairs. Check with, and get an estimate from, one or more qualified mitigators before fixing.

b. What Are Radon-Resistant Features?

Radon-resistant techniques (features) may vary for different foundations and site requirements. If you’re having a house built, ask your builder if they’re using EPA’s recommended approach (International Residential Code, Appendix F, or ASTM E 1465-08). If your new house was built (or will be built) to be radon-resistant, it will include these basic elements:

The techniques may vary for different foundations and site requirements, but the basic elements are:

A. Gas Permeable Layer
This layer is placed beneath the slab or flooring system to allow the soil gas to move freely underneath the house. In many cases, the material used is a 4-inch layer of clean gravel. This gas-permeable layer is used only in homes with casement and slab-on-grade foundations; it is not used in homes with crawlspace foundations.
house cut away
B. Plastic Sheeting
Plastic sheeting seams sealed is placed on top of the gas permeable layer and under the slab to help prevent the soil gas from entering the home. In crawlspaces, the sheeting is placed over the crawlspace floor.
C. Sealing and Caulking
All below-grade openings in the concrete foundation floor are sealed to reduce soil gas entry into the home.
D. Vent Pipe
A 3- or 4-inch gas-tight or PVC pipe (or other gas-tight pipe) runs from the gas permeable layer through the house to the roof to safely vent radon and other soil gases above the house.
E. Junction Box
An electrical junction box is included in the attic to make the wiring and installation of a vent fan easier. For example, you decide to activate the passive system because your test result showed an elevated radon level (4 pCi/L or more). A separate junction box is placed in the living space to power the vent fan alarm. An alarm is installed along the vent fan to indicate when the vent fan is not operating properly.