The homeowner’s reference
How often should you test for radon? 5 situations to consider
Test if your home's radon history is unknown. For a home with a mitigation system, EPA recommends retesting at least every two years. Buying or selling, renovations and changes in how you use a lower level are also reasons to revisit testing; ask your state program about the guidance for your home.
Sources: CDC: Testing Your Home for Radon; EPA: Checking whether a mitigation system works.
1. You do not have a usable test history
Start by looking for a report for this home. A conversation with a neighbor or a general radon map does not tell you what a test would find inside your building. If you cannot establish the home's radon level, arrange a test.
When you receive the report, save the date, location within the home, method and result. Those details make a future discussion with a tester more useful.
Sources: EPA: Home Buyer's and Seller's Guide to Radon (2024, PDF).
2. You are preparing to buy or sell
Review any previous result early enough to discuss it during the transaction. Ask when and where the test was taken and whether the home has changed since then. EPA's home-buyer guide explains why a buyer may request another measurement even when a previous report exists.
Share the transaction deadline with the tester before agreeing to an appointment. Recommendations for testing and a legal requirement to test are different questions; confirm local requirements separately.
Sources: EPA: Home Buyer's and Seller's Guide to Radon (2024, PDF).
3. You are planning or have finished renovations
CDC recommends testing before and after renovations. Keep the earlier report so you can discuss any changed result with your tester. Do not assume that a measurement from before the work still describes the home afterward.
Sources: CDC: Testing Your Home for Radon.
4. You will spend more time on a lower level
A basement becoming a bedroom or home office changes how the space is used. CDC identifies increased use of a lower level as a reason to test. Tell the tester which rooms will be occupied so the measurement plan fits the change.
Sources: CDC: Testing Your Home for Radon.
5. You have a radon mitigation system
Keep both the post-installation report and later radon results. EPA recommends retesting at least every two years after mitigation. North Carolina DHHS also advises retesting after significant building alterations and following state or local guidance.
If a system warning device changes, arrange attention to the system rather than waiting for the next calendar reminder. Use a radon measurement to establish the concentration; a fan gauge serves a different purpose.
Sources: EPA: Checking whether a mitigation system works; North Carolina DHHS: Radon Mitigation; EPA: Consumer's Guide to Radon Reduction (2025, PDF).
Build a test record you can use again
- Keep the complete report, not just the result number.
- Record the test location and dates.
- Keep notes about building changes and mitigation work.
- Ask the tester when another measurement is appropriate.
- Save the next reminder with your household maintenance records.
Find a credentialed provider
Find a testing provider through the state and city directory. Check the official credential record, then explain your test history and any changes to the home.
Find providers in your area · Check credentials by state
Testing instructions and requirements depend on the test, building and jurisdiction. Use the linked agency guidance and your qualified professional’s instructions for your situation.