Radon Levels by Floor: Basement vs. Upper Floors
Radon enters a home from the soil beneath it, so concentrations are almost always highest in the basement or lowest livable level and decrease at each floor above it as the gas disperses through the building's air volume. The EPA specifically recommends testing the lowest livable level of the home, meaning a room used regularly, not an unfinished crawlspace or unused area.
This floor-to-floor gradient is also why a system designed and installed by a certified professional accounts for how air actually moves through the specific house, rather than assuming one universal fix works the same in a ranch, a two-story colonial, and a home with a walkout basement.
If a family spends significant time in a finished basement, whether as a living room, home office, or a child's playroom, that level deserves the same testing priority as any other regularly used room in the house, regardless of overall square footage above it.
Common questions
If the basement is unfinished and unused, should the first floor be tested instead?
The EPA's guidance is to test the lowest level that is lived in, so if the basement genuinely is not used as living space, the first floor becomes the relevant test location; but a basement being finished or used even occasionally usually changes that answer.
Can upper-floor levels still be a concern even if they are lower?
Yes, if the basement or first-floor level is meaningfully elevated, upper floors can still carry enough radon to matter, particularly with a home that has significant airflow between floors via stairwells or an open floor plan.
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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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