EPA radon guidance

EPA's recommendations come down to testing, then acting on the number. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. EPA's action level page gives the reason for the second step: because there is no known safe level of exposure to radon, EPA also recommends that Americans consider fixing their home for radon levels between 2 pCi/L and 4 pCi/L.

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2 pCi/L

4 pCi/L

00 Bq/m³274 Bq/m³4148 Bq/m³6222 Bq/m³8296 Bq/m³10+370 Bq/m³

• Below 2 pCi/L (below 74 Bq/m³)Below both of EPA's guidance levels.
• 2 to 4 pCi/L (74 Bq/m³ to 148 Bq/m³)EPA recommends considering a fix when the level is between 2 and 4 pCi/L.
• At or above 4 pCi/L (148 Bq/m³ and up)EPA recommends fixing a home when the radon level is 4 pCi/L or higher.

The action level page adds context for the numbers. The average indoor radon concentration for America's homes is about 1.3 pCi/L (50 Bq/m3), and it is upon this national average that EPA based its estimate of 21,000 radon-related lung cancers a year. The average concentration of radon in outdoor air is 0.4 pCi/L (15 Bq/m3), or one tenth of EPA's 4 pCi/L action level. EPA notes that most countries' action levels are similar to the 4 pCi/L level recommended in the United States.

EPA's testing steps

1. 1

   Take a short-term test

   A Citizen's Guide to Radon says short-term tests remain in your home for two days to 90 days, depending on the device. Place it in the lowest lived-in level of the home, at least 20 inches above the floor. See how to test.

2. 2

   Follow up if the result is 4 pCi/L or more

   EPA's Step 2 is to follow up with either a long-term test or a second short-term test: a long-term test for a better understanding of your year-round average, a second short-term test if you need results quickly.

3. 3

   Fix the home when the follow-up confirms it

   Fix your home if your long-term test result is 4 pCi/L or more; with two short-term tests, consider fixing if their average is 4 pCi/L or more. EPA says to use a contractor who is trained to fix radon problems. See radon mitigation.

4. 4

   Test again after the fix, and later

   EPA says to test your home again after it is fixed, and that it is a good idea to retest every two years to be sure radon levels remain low.

A Citizen's Guide to Radon describes two general ways to test. Short-term tests remain in your home for two days to 90 days, depending on the device; charcoal canisters, alpha track, electret ion chamber, continuous monitors and charcoal liquid scintillation detectors are the ones it says are most commonly used. Long-term tests remain in your home for more than 90 days, and alpha track and electret detectors are commonly used for this type of testing. The guide says a long-term test will give you a reading that is more likely to tell you your home's year-round average radon level than a short-term test.

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Test	How long it runs	What it is for
Short-term test	Stays in the home from 2 to 90 days, depending on the device, and for a minimum of 48 hours.	A faster screening result. Because radon levels vary from day to day and season to season, it is less likely than a long-term test to tell you the year-round average.
Long-term test	Stays in the home for more than 90 days.	It is more likely than a short-term test to tell you the home's year-round average radon level.
Continuous monitor	Logs readings for the whole test, run as a short-term or a long-term test under the same durations in EPA guidance.	Logs a graph over time, so you can see trends and spot anomalies rather than a single number.

Closed-house conditions, in EPA's words

A home sale follows a separate set of steps. EPA's Consumer's Guide to Radon Reduction says EPA recommends two categories of radon testing: one for concerned homeowners or occupants whose home is not for sale, covered by the Citizen's Guide, and one for real estate transactions, covered by the Home Buyer's and Seller's Guide. It also says all radon tests should be taken for a minimum of 48 hours. Compare devices on the radon test kits page.

EPA's guidance leans on a health finding it shares with the Surgeon General. A Citizen's Guide to Radon says the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States today, and that EPA and the Surgeon General recommend testing all homes below the third floor for radon. EPA also recommends testing in schools.

Surgeon General advisory: radon and the 2005 warning

EPA's Health Risk of Radon page records that on January 13, 2005, Richard H. Carmona, the U.S. Surgeon General, issued a national health advisory on radon. The page says he urged Americans to test their homes to find out how much radon they might be breathing, and stressed the need to remedy the problem as soon as possible when the radon level is 4 pCi/L (150 Bq/m3) or more. The Citizen's Guide prints the advisory's closing lines: radon can be detected with a simple test and fixed through well-established venting techniques.

Where EPA's risk estimate comes from

The Health Risk of Radon page says radon is responsible for about 21,000 lung cancer deaths every year, and that about 2,900 of these deaths occur among people who have never smoked. EPA's 2003 Assessment of Risks from Radon in Homes put its best estimate at about 21,000, with an uncertainty range of 8,000 to 45,000, and the Citizen's Guide says EPA's revised estimates are based on the National Academy of Sciences BEIR VI report, which concluded that radon is the second leading cause of lung cancer after smoking.

EPA's page on how we know radon is a carcinogen says the World Health Organization, the National Academy of Sciences, the US Department of Health and Human Services and EPA have classified radon as a known human carcinogen. It cites an international study, led by the National Cancer Institute, of data on 68,000 underground miners who were exposed to a wide range of radon levels, and notes that the lung cancer risk in miners has been documented at exposure levels comparable to those which occur in homes. More on the health side is in the radon and lung cancer guide.

EPA puts its risk estimate in a chart that the Citizen's Guide and the Health Risk of Radon page both carry: if 1,000 people were exposed to a given level over a lifetime, about how many could get lung cancer. The figures come from EPA's 2003 Assessment of Risks from Radon in Homes. At 4 pCi/L the Citizen's Guide gives about 62 people who smoked and about 7 people who never smoked.

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EPA estimate, lifetime exposure

• Out of 1,000 people who smoked
• Out of 1,000 people who never smoked

About how many people out of 1,000 exposed over a lifetime could get lung cancer, by radon level

Radon level	Could get lung cancer, per 1,000	What to do
20 pCi/L740 Bq/m³	Smoked: About 260Never smoked: About 36	Fix your home
10 pCi/L370 Bq/m³	Smoked: About 150Never smoked: About 18	Fix your home
8 pCi/L300 Bq/m³	Smoked: About 120Never smoked: About 15	Fix your home
4 pCi/L150 Bq/m³	Smoked: About 62Never smoked: About 7	Fix your home
2 pCi/L75 Bq/m³	Smoked: About 32Never smoked: About 4	Consider fixing between 2 and 4 pCi/L
1.3 pCi/L50 Bq/m³	Smoked: About 20Never smoked: About 2	Average indoor radon level
0.4 pCi/L15 Bq/m³	Smoked: About 3Never smoked: No figure given	Average outdoor radon level

• Smoked: If you are a former smoker, your risk may be lower.
• Never smoked: If you are a former smoker, your risk may be higher.
• Reducing radon levels below 2 pCi/L (75 Bq/m3) is difficult.
• Lifetime risk of lung cancer deaths, as EPA estimates it.

The Citizen's Guide says your chances of getting lung cancer from radon depend mostly on how much radon is in your home, the amount of time you spend in your home, and whether you are a smoker or have ever smoked. It adds that not everyone exposed to elevated levels of radon will develop lung cancer, and that the amount of time between exposure and the onset of the disease may be many years. EPA also concluded that the effects of radon and cigarette smoking are synergistic, so that smokers are at higher risk from radon.

EPA publishes a short list of guides for homeowners, and each one answers a different question. Its publications page describes them, and the table below uses those descriptions.

A Citizen's Guide to Radon: the EPA guide to radon testing

The Citizen's Guide is the one to read first. It opens with EPA's three recommendations: test your home for radon, fix your home if your radon level is 4 picocuries per liter (pCi/L) or higher, and know that radon levels less than 4 pCi/L still pose a risk and in many cases may be reduced. It has sections on how to test your home, what your test results mean, radon in water, how to lower the radon level in your home and the risk of living with radon, and a section of radon myths and facts.

The Consumer's Guide and the Home Buyer's and Seller's Guide

EPA's publications page says the Consumer's Guide to Radon Reduction has been specifically designed for people who have tested their home and confirmed that they have elevated radon levels, 4 pCi/L (150 Bq/m3) or higher. The Home Buyer's and Seller's Guide is intended for anyone who is buying or selling a home, real estate and relocation professionals, home inspectors and others. For a sale, start with the buying a house with radon guide.

Building Radon Out, for new homes

For new construction, the Citizen's Guide refers readers to EPA's Building Radon Out: A Step-by-Step Guide on How to Build Radon-Resistant Homes. It says radon-resistant construction techniques can be effective in preventing radon entry, that every new home should be tested after occupancy even if it was built radon-resistant, and that if radon levels are still in excess of 4 pCi/L the passive system should be activated by having a qualified mitigator install a vent fan. See radon-resistant new construction.

The Consumer's Guide to Radon Reduction is EPA's guide for this step. It says EPA recommends fixing your home if the results of one long-term test or the average of two short-term tests show radon levels of 4 pCi/L or more, and that with today's technology radon levels in most homes can be reduced to 2 pCi/L or below. Of the methods, it says EPA generally recommends methods that prevent the entry of radon.

The Consumer's Guide calls active subslab suction the most common and usually the most reliable radon reduction method, and says submembrane suction, when properly applied, is the most effective way to reduce radon levels in crawlspace homes. It is specific about sealing: EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently.

Choosing a contractor the way EPA describes

1. 1

   Start with your state radon office

   The Consumer's Guide says many states require radon professionals to be licensed, certified or registered. See state radon programs and the mitigation professionals directory.

2. 2

   Get more than one estimate

   It is wise to get more than one estimate, to ask for references, and to contact some of those references, the guide says.

3. 3

   Check what the proposal includes

   The guide's checklist asks about diagnostic testing before design, a warning device to caution you if the system is not working correctly, testing after installation, and a guarantee to reduce radon levels to 4 pCi/L or below, and for how long.

4. 4

   Test after the system is running

   A post-mitigation radon test should be done within 30 days of system installation, but no sooner than 24 hours after your system is in operation with the fan on, and EPA recommends an independent follow-up measurement as well.

5. 5

   Keep testing

   The Consumer's Guide says it is a good idea to retest your home at least every two years to be sure radon levels remain low.

EPA's Home Buyer's and Seller's Guide says its radon testing guidelines have been developed specifically to deal with the time-sensitive nature of home purchases and sales, and the potential for radon device interference, which is why they differ slightly from the guidelines in EPA's other publications. For sellers, EPA recommends that you test your home before putting it on the market and, if necessary, lower your radon levels, and says saving the results and what was done to fix any problems could be a positive selling point. For buyers, 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, and if the home has not yet been tested, have the house tested.

The guide also recommends testing a home in the lowest level that could be used regularly, since a buyer may choose to live in a lower area of the home than that used by the seller, and says any real estate test for radon should include steps to prevent or detect interference with the test device. It suggests the contract specify where the test will be located, who should conduct it, what type of test to do, when to do it, how the seller and the buyer will share the results and costs, and when radon mitigation measures will be taken, and who will pay for them. The buying a house with radon and selling a house with radon guides go step by step.

EPA's Map of Radon Zones page says the map was developed in 1993 to identify areas of the U.S. with the greatest potential for elevated indoor radon levels, and that it should not be used to determine if individual homes need to be tested. Its advice is plain: no matter where you live, test your home for radon.

The same page says the map is based on indoor radon measurement data, geology, aerial radioactivity, soil parameters, and foundation types, and that it can be supplemented with available state-developed or other data to further understand the radon potential for a specific area. For measured data it points to the CDC Environmental Health Tracking Network, which is where Radon411's county testing figures come from.

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Predicted potential

Counties per EPA radon zone

Zone	Bar	Counties	Share of all counties
Zone 1Highest predicted potential		1,071	33.1%
Zone 2Moderate predicted potential		1,034	32.0%
Zone 3Lower predicted potential		1,033	32.0%
No zoneNo EPA zone on file		93	2.9%

3,231 counties in all.

An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.

EPA's publications page says the purpose of the map is to assist national, state and local organizations to target their resources and to implement radon-resistant building codes. It adds that the map is not intended to be used to determine if a home in a given zone should be tested for radon, that homes with elevated levels of radon have been found in all three zones, and that all homes should be tested regardless of geographic location.

The Citizen's Guide closes with a page of radon myths and facts. The table sets each myth beside EPA's answer, in the guide's words.

On water, the guide's answer is an order of steps rather than a yes or no: although radon gets into some homes through water, it is important to first test the air in the home for radon. If your water comes from a public water system that uses ground water, call your water supplier; if high radon levels are found and the home has a private well, the Safe Drinking Water Hotline at (800) 426-4791 has information on testing your water. More claims are weighed in the radon scam guide.

Standards of practice

EPA's current standards of practice are industry consensus standards. Its standards of practice page says that since about 2012 EPA has been actively participating in the radon industry led ANSI/AARST voluntary consensus-based standards process, and that the Federal government's reliance on privately developed voluntary consensus based standards is to be preferred over the Federal government developing such standards. The page lists the current ANSI/AARST standards, including the home measurement protocol (MAH-2023) and the soil gas mitigation standard for existing homes (SGM-SF-2023).

The National Radon Action Plan

EPA's National Radon Action Plan page describes a collaborative effort between eleven organizations dedicated to eliminating avoidable radon-induced lung cancer in the United States, led by the American Lung Association. In 2015 the partners set a goal to mitigate 5 million high-radon homes and save 3,200 lives annually by 2020, by building radon testing and mitigation into the systems that govern purchasing, financing, constructing and renovating buildings. It grew out of the Federal Radon Action Plan, a 2010 to 2016 federal effort.

What is on www.epa.gov/radon

EPA's radon home page links its risks and solutions pages, the National Radon Action Plan, standards of practice, frequently asked questions, the State and Tribal Indoor Radon Grants (SIRG) program, outreach and media, and regional and state contacts, where EPA says you can find out which radon zone you live in. For state programs in one place, see state radon programs.

EPA's program is large, but what it asks of a household is short. Test the home, because testing is the only way to know. Follow up a high short-term result before deciding. Fix the home when the result calls for it, using a qualified contractor, and test again afterward.

EPA's test kit page says free test kits are sometimes available from local or county health departments, or from state radon programs. Compare kit types on the radon test kits page, or find a certified tester through the radon professionals directory.

On retesting, EPA's page on how often to test quotes the Citizen's Guide: if your living patterns change and you begin occupying a lower level of your home, such as a basement, you should retest on that level, and even if your result is below 4 pCi/L you may want to test again sometime in the future. More on timing is in how often should I test.