Short-term vs long-term radon tests
How long each radon test runs, which devices are used, and when to follow up.
Short-term tests
Short-term tests run 2 to 90 days. Common devices are charcoal kits, liquid scintillation kits, electret chambers and electronic continuous monitors. They're the quickest way to see whether a home has a radon problem, but they reflect conditions only during the test. For short-term tests, NH DHHS says to close windows for 12 hours before and during the test. The free NH state kit is a charcoal kit exposed for 48 to 96 hours.
Long-term tests
Long-term tests run more than 90 days and up to a year, using alpha-track kits, electret chambers or continuous monitors. Because radon changes daily and seasonally, a long-term test gives a better idea of your year-round average, and you don't need to keep the house closed up.
Which should you use?
- First screen: a short-term test.
- Result of 4 pCi/L or more: follow up. EPA suggests a long-term test, or a second short-term test if you need results quickly.
- Real estate sale: usually short-term, with two kits side by side (see our buying and selling guide).
See the kit comparison for lab fees and turnaround.
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)
- Radon testing when buying or selling a home in NH
- Radon in well water in New Hampshire
- Radon mitigation basics
- When to retest for radon
Sources
Sources checked October 31, 2026. Spot an error? Send a correction.