How Often Should You Retest for Radon?
The EPA recommends retesting every two years even without any change to the home, since radon levels can shift with soil conditions, weather patterns and structural settling over time. Retesting sooner is recommended after any renovation that affects the foundation, after adding or sealing a crawlspace, or after any change to HVAC or ventilation that could affect how air moves through the lower level.
Renovations are the most commonly overlooked trigger for retesting. Finishing a basement, sealing a previously vented crawlspace, or even significant landscaping and grading changes near the foundation can all change how soil gas moves into the house, sometimes for the worse even in a home that tested fine years earlier.
A short-term test is usually sufficient to answer whether a retest after a specific change or a two-year interval still reads below the action level; see our page on short-term vs. long-term testing for how to choose between them.
Common questions
Does having a mitigation system already installed change this?
A working system should be checked with its own periodic maintenance rather than a full retest, but a general retest is still a reasonable idea after major renovations even with a system in place, to confirm it is still performing as expected under the new conditions.
Is a two-year interval really necessary if the last result was very low?
The EPA's general guidance applies regardless of a prior low result, since conditions genuinely can change. A homeowner more risk-tolerant with a very low prior result might reasonably choose a longer interval, but that is a personal risk decision, not what the guidance itself recommends.
Have a number you want read?
Tell us the result and your town in York County, or call and read it out. We will tell you what it points to and what a system would involve in a house like yours.
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