Radon guide
When to retest for radon
How often to retest your home for radon, including after renovations and after mitigation.
- Every 2 years: NH DPH recommends testing at least every 2 years, even after a low result.
- After construction: NH DPH recommends testing after construction on or around the property, such as a renovation, addition or finishing a basement.
- After a summer test: if you tested in warm months with windows open, NH DHHS suggests testing again in colder months.
- After mitigation: EPA recommends testing after a system is installed to confirm it works, then periodically after that.
- Private well under 4,000 pCi/L: NHDES recommends retesting air and water every 3 to 5 years.
Short on budget? NH residents can use the free state kit, or borrow a library monitor to check different rooms and seasons.
In New Hampshire? Order a free state test kit or see radon by NH county.
More guides
- How to read a radon test result (pCi/L)
- Short-term vs long-term radon tests
- Radon testing when buying or selling a home in NH
- Radon in well water in New Hampshire
- Radon mitigation basics
Sources
- NH DHHS Radon Program data brief, July 2026
- NH DHHS, Testing for Radon
- EPA, A Citizen's Guide to Radon
- NHDES fact sheet WD-DWGB-3-12, Radon in Your Home
Sources checked October 31, 2026. Spot an error? Send a correction.