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Should I test for radon?

By Radon411 Editorial TeamUpdated How we research

Short answer

Yes. EPA and the Surgeon General recommend testing every home below the third floor, whatever its age, foundation or location, because radon cannot be seen, smelled or tasted, and a test, which is inexpensive and takes only a few minutes of your time, is the only way to know a home's level.

Next step: pick the right test for your home. Which test to use

Is radon testing really necessary if nobody in the house feels unwell? Yes. Radon gives no warning: it has no color, smell or taste, and it is the second leading cause of lung cancer in the United States. Testing is the only way to know your level of exposure, and all homes should be tested.

Any home can have a radon problem: new and old homes, well-sealed and drafty homes, and homes with or without basements. High radon levels have been found in every state, and homes with elevated levels have been found in all three of EPA's radon zones, so neither a map nor a neighbor's result can stand in for a test of your own home.

Good times to test are now, if the home has never been tested; before buying or selling; before and after a renovation; after a system is installed; and again some time after a low result.

What to do next: choose a kit or book a measurement professional, test the lowest lived-in level, and read your result with the interpreter.

Is radon testing really necessary?

It is, because nothing else tells you. Radon gives no sign of itself: you can't see it, smell it or taste it, and testing is the only way to know whether you and your family are at risk. The usual reasons for skipping a test do not hold up.

Common reasons for not testing, and the facts
The reasonThe facts
"Testing is difficult, slow and expensive."Radon testing is easy. You can test your home yourself or hire a qualified radon test company, and either approach takes only a small amount of time and effort.
"Radon only affects certain kinds of homes."Radon can be a problem in homes of all types: old homes, new homes, drafty homes, insulated homes, homes with basements and homes without basements.
"Radon is only a problem in some parts of the country."High radon levels have been found in every state. Radon problems vary from area to area, but the only way to know your radon level is to test.
"My neighbor tested and was fine."A neighbor's result is not a good guide. Radon levels can vary greatly from home to home.
"I've lived here so long it is too late."You reduce your risk of lung cancer when you reduce radon levels, even if you've lived with a radon problem for a long time.

The stakes are why the point is pressed. Radon is the second leading cause of lung cancer in the United States, and nearly 1 out of every 15 homes in the U.S. is estimated to have elevated radon levels. Your chance of getting lung cancer from radon depends mostly on how much radon is in your home, the amount of time you spend there, and whether you smoke or have ever smoked. Only a test answers the first of those.

Which homes to test

The answer is broad on purpose. EPA and the Surgeon General recommend testing all homes below the third floor for radon, and EPA recommends testing schools too. The table shows how that applies to the homes people ask about most.

Testing by kind of home
Your homeWhat to do
A house with a basementTest the lowest lived-in level: the basement if it is frequently used, otherwise the first floor.
A house on a slab or over a crawlspaceTest it: any home may have a radon problem, with or without a basement. See radon testing without a basement.
An apartment or condoTest it if it is below the third floor.
A new home, even one built radon-resistantTest it after you move in.
A home you are buying or sellingHave it tested for radon before the sale.
A home with a radon reduction systemRetest at least every two years to be sure radon levels remain low.
A home on a private wellTest the air first; if the air is high and the water comes from a well, have the water tested.

When to test

If the home you live in has never been tested, the answer is now. After that, a handful of moments call for a new test, because the home's radon level may have changed or someone needs a current answer.

Moments that call for a radon test
WhenWhy
Before sellingFixing a problem before the home goes on the market leaves more time to deal with it.
Before buyingYou should know the indoor radon level of any home you consider buying.
Before and after a renovationTest an area before a major renovation, such as finishing a basement, and test again after the work is completed.
When you start using a lower floorIf you begin living on a lower level, such as a basement, retest on that level.
After a radon system is installedTest again to be sure radon levels have been reduced.
Some time after a low resultEven a result below 4 pCi/L is worth checking again sometime in the future.

Repeat testing has its own page: see how often you should test for the intervals, and when you should test for the season and conditions.

What a test involves

A test is a small device left in one room, then read by a lab or by the device itself. Low-cost do-it-yourself kits are sold by mail and in some hardware stores and other retail outlets, and you can hire a qualified tester instead if you prefer, or if you are buying or selling a home.

Table comparing a short-term radon test, a long-term radon test and a continuous radon monitor: how long each runs and what each is for.
Read this figure as text
TestHow long it runsWhat it is for
Short-term testStays 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 testStays 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 monitorLogs 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.
The three kinds of radon test: short-term, long-term and continuous monitors.
  • How long: stay in the home for two days to 90 days, depending on the device, and for more than 90 days. Every radon test should run for a minimum of 48 hours.
  • Where: the lowest lived-in level of the home, in a room used regularly but not the kitchen or bathroom, at least 20 inches above the floor.
  • Conditions: for a short-term test, keep windows and outside doors closed as much as possible, and for a test of just 2 or 3 days close them at least 12 hours before it starts.
  • Results: a mailed kit's results usually arrive within a few weeks.

The full method, step by step, is on how to test for radon, and kits are compared on radon test kits.

What your result tells you to do

A test is worth doing because the number leads somewhere. EPA recommends fixing a home when the radon level is 4 or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. A single short-term result at or above that line is confirmed first, with a long-term test or a second short-term test.

Flowchart of EPA's radon testing steps: take a short-term test; at or above 4 pCi/L follow up with a long-term or a second short-term test; then fix the home or consider fixing based on the result or the average of the two tests.
Read this figure as text

  1. 1Step 1: Take a short-term test.

    • Below 4 pCi/LEven if your test result is below 4 pCi/L, you may want to test again sometime in the future.
    • At or above 4 pCi/LIf your result is at or above 4 pCi/L, take a followup test to be sure.

  2. 2Step 2: Follow up with either a long-term test or a second short-term test.

    • Long-term testFor a better understanding of your year-round average radon level, take a long-term test.
    • Second short-term testIf you need results quickly, take a second short-term test. If your first short-term test result is more than twice EPA's 4 pCi/L action level, you should take a second short-term test immediately.

  3. 3Step 3: Decide whether to fix your home.

    • After a long-term testFix your home if your long-term test result is 4 pCi/L or more.
    • After a second short-term testConsider fixing your home if the average of your first and second test is at or above 4 pCi/L.
The testing steps: a short-term test, a follow-up when the first result is high, then a decision on the long-term result or the average of two short-term tests.

For scale, EPA estimates the average indoor radon level at about 1.3 pCi/L, against about 0.4 pCi/L in outdoor air. Any radon exposure carries some risk, and most homes today can be brought down to 2 pCi/L or below. Use the result interpreter to read a number against EPA's guidance.

Questions about whether to test

Is radon testing worth it?

It is a small effort for an answer you cannot get any other way. Testing is inexpensive and easy, should take only a few minutes of your time, and is the only way to know whether you are at risk from radon.

Do I need a radon test if I don't have a basement?

Yes. Any home may have a radon problem, with or without a basement. Test the lowest lived-in level, which in a house with no basement is usually the first floor. The page on testing without a basement covers slabs and crawlspaces.

Should I test a condo or apartment for radon?

If it is below the third floor, yes: EPA and the Surgeon General recommend testing all homes below the third floor. Basements and first floors typically have the highest radon levels because they are closest to the ground.

Should I test for radon before buying a home?

Yes. You should know the indoor radon level of any home you consider buying, and anyone buying or selling a home should have it tested. See should you buy a house with radon for what to do with the result.

Should I test my water for radon?

Test the air first. If the air shows a radon problem and your water comes from a well, have the water tested too. The page on testing well water for radon explains how.

Should I test again after a low result?

At some point, yes. Even a result below 4 pCi/L is worth checking again sometime in the future, and you should retest if you start living on a lower level of the home.

Should I test myself or hire someone?

Either works for your own home: a do-it-yourself kit, or a qualified tester if you prefer, or if you are buying or selling. The radon scam guide covers how to check a tester's credentials.

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