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Radon testing
How Often Should You Test for Radon?
Use occupancy changes, renovations, transactions and mitigation-system maintenance to decide when a previous radon result needs a new test.
Quick answer
If your home has a radon mitigation system, the EPA recommends retesting at least every two years. Check the system warning device regularly as well. A new measurement can also be useful when people begin using a lower level, the home has been renovated or altered, or a buyer needs to decide whether an older result still represents the property.
Find your last report and check where the device was placed. Then use the situations below to see whether that result still fits how you use the home.
Which retest situation applies?
| Situation | Reason to consider a new test | What to check first |
|---|---|---|
| Home with a mitigation system | Confirm that radon levels remain low after the system has been operating. | Warning device status, last test date and any system service history. |
| Lower level becomes living space | The previous measurement may not represent where people now spend time. | Where the earlier device was placed and how the lower level is now used. |
| Renovation or alteration | Changes to the home can make an older result less useful for the current conditions. | What changed, when work occurred and where the previous test was conducted. |
| Home purchase or sale | A buyer may need a current, properly conducted result for the decision. | Report date, test conditions, checklist compliance and transaction deadline. |
For a home with a mitigation system
- Look at the warning device. Check it regularly and follow the system provider’s instructions if it indicates a problem.
- Find the last radon report. Note the date, result, device location and whether the test occurred after mitigation was installed.
- Plan routine confirmation. The EPA advises retesting a mitigated home at least every two years to confirm levels remain low.
- Report changes. Tell the testing team about renovations, foundation work or changes in how lower levels are occupied.
If the warning device shows a problem, do not wait for the next routine measurement to address it. The warning device and the radon test have related but different roles: one indicates system operation, while the other measures radon under the test conditions.
When living patterns change
The EPA recommends retesting when people begin occupying a lower level that the previous measurement did not cover. This may apply when a basement becomes a bedroom, office, playroom or other regularly used space.
For example, a previous device placed upstairs may have answered an earlier question but may not represent the lower level now used every day. Bring the prior report and explain which rooms have changed. The testing team can then plan a measurement around current occupancy rather than relying only on the age of the old result.
For a purchase or sale
The EPA says a buyer may request a new test when the previous test is not recent, for example, when it was not performed within the last two years. A buyer may also request another measurement when the earlier test checklist was not followed, the home has been renovated or altered, or planned occupancy includes a lower level that was not tested.
The two-year example helps a buyer and seller judge whether an existing report still represents the property. It is not a universal federal retest law. State or local disclosure requirements and the terms of the transaction may create separate considerations.
Share the transaction deadline before scheduling. The team can explain the testing process and available appointment times.
What a radon result does and does not establish
- It does: Measure radon for the location, period and conditions represented by the test.
- It does: Help you and the testing professional decide whether further action is needed.
- It does not: Guarantee that the level will never change.
- It does not: Represent a newly occupied lower level if that area was not part of the earlier measurement.
- It does not: Replace regular checks of a mitigation system’s warning device.
Even after a result below 4 pCi/L, the EPA says a homeowner may want to test again in the future.
Have these details ready
- Your prior report, result and test date.
- The room and floor where the device was placed.
- Renovations, foundation work or changes in lower-level use.
- Whether a mitigation system is present and what its warning device shows.
- Any purchase, sale or other deadline that affects timing.
Learn about NextDay Inspect’s radon testing service or review the radon guide for home buyers and sellers.
Book your next radon test
If you need to check the current radon level, schedule a radon test. Use the quote form if you need help coordinating radon with another inspection service.
Sources and further reading
EPA: How often should I test/retest my home for radon? and EPA: How do I know if my radon mitigation system is working properly?