How Often Should You Test for Radon?
The EPA says to retest at least every two years if you have a radon system. See when to test again without one, including after renovations or a move.
How often you should test for radon depends on your home: with a radon reduction system, the EPA says it’s a good idea to retest at least every two years. Without a system, the guides used here set no fixed schedule. If your result was below 4 pCi/L (148 Bq/m³), the EPA says you may want to test again sometime in the future, and you should test again when your home or how you use it changes. If you have never tested, start now.
This guide follows U.S. EPA guidance. Other countries and some local rules may differ, so check your national or local guidance if you live outside the United States.
When to test for radon
| Your situation | When to test | EPA source |
|---|---|---|
| Never tested | Now | Citizen’s Guide |
| New home, including one with radon-resistant features | After you move in | Consumer’s Guide |
| First short-term result of 4 pCi/L (148 Bq/m³) or higher | Follow up with a long-term or second short-term test | Citizen’s Guide |
| First short-term result above 8 pCi/L (296 Bq/m³) | Second short-term test immediately | Citizen’s Guide |
| Radon system just installed | Within 30 days, but no sooner than 24 hours after it starts running | Consumer’s Guide |
| Radon system in place | At least every two years | Consumer’s Guide |
| Started using a lower level, such as a basement | Retest on that level | Citizen’s Guide |
| Major renovation | Before you begin in the affected area, and again after the work is finished | Citizen’s Guide |
| Result below 4 pCi/L (148 Bq/m³) and nothing has changed | You may want to test again sometime in the future | Citizen’s Guide |
| Selling a home | Consider a new test if the last one isn’t recent, for example within two years | Home Buyer’s and Seller’s Guide |
If you have never tested
The EPA says all homes should be tested. You can’t estimate your level from the area you live in, because it says homes next to each other can have different indoor radon levels. Testing is the only way to find out.
See How to Test for Radon to get started.
If you have a radon reduction system
Testing once isn’t the end of it. The EPA says a post-mitigation test should be done within 30 days of system installation, but no sooner than 24 hours after the system is in operation with the fan on, if it has one. After that, it says it’s a good idea to retest at least every two years to be sure radon levels remain low.
Between tests, look at the system’s warning device, usually a manometer, on a regular basis. If it shows the system isn’t working properly, call a contractor. The fan should never be turned off, because it must run continuously for the system to work correctly.
If your home has no system and your result was low
This is where general advice is often less precise than the source. The EPA’s “every two years” guidance appears in its discussion of homes with a radon reduction system. For a home without one and a result below 4 pCi/L (148 Bq/m³), the Citizen’s Guide says only that you may want to test again sometime in the future.
A simple habit, if you want one: some homeowners may find it easiest to use the same two-year reminder. That is our suggestion, not an EPA requirement. Test sooner if anything in the next section applies.
If your result was between 2 pCi/L (74 Bq/m³) and 4 pCi/L (148 Bq/m³), the EPA says no level of radon is safe and that you may want to consider fixing your home. See How to Read Radon Test Results.
What should prompt a new test
You start using a lower level. If your living patterns change and you begin occupying a lower level, such as a basement, the EPA says to retest on that level.
You renovate. The EPA says major renovations can change the radon level in any home. If you plan a major structural renovation, such as converting an unfinished basement into living space, test the area before you begin, and test again after the work is completed. If you already have a radon system, it says to retest in the lowest lived-in area after you remodel to make sure the construction didn’t reduce its effectiveness.
You are selling or buying. The EPA says a potential buyer may ask for a new test, especially if the last test isn’t recent, the home has been renovated or altered since the test, or the buyer plans to use a lower level than the one tested. See Radon Test for Home Inspection.
Does the time of year matter?
Radon levels tend to vary from day to day and season to season. A short-term test is a snapshot of those days, so it is less likely than a long-term test to tell you your year-round average. If you want a better picture of that average, use a long-term test, which runs for more than 90 days. See Short-Term vs Long-Term Radon Testing and Why Radon Levels Change.
A continuous digital monitor can help you see how readings change between tests. It complements, but does not replace, professional radon testing or mitigation. If readings stay at or above 4 pCi/L (148 Bq/m³), contact a qualified radon professional.
Frequently asked questions
Should you test for radon every year?
How often should you test for radon after mitigation?
Do new homes need radon testing?
Is an old radon test still good when selling a home?
Sources
- A Citizen's Guide to Radon — U.S. EPA
- A Consumer's Guide to Radon Reduction — U.S. EPA
- Home Buyer's and Seller's Guide to Radon — U.S. EPA