Is radon common in Lancaster County and southeastern PA?
Yes. Pennsylvania has some of the highest indoor radon levels in the United States, and a large share of homes tested in Lancaster, Berks, Chester and York counties come back above the EPA action level of 4.0 pCi/L. The Reading Prong, which runs through Berks, Montgomery and Lehigh counties, is one of the best-known high-radon geologic formations in the country.
Why the levels are high here
Radon is a naturally occurring gas produced as uranium in soil and bedrock decays. Fractured limestone, shale and the granitic rock of the Reading Prong all release it, and it enters homes through basement floor cracks, sump pits, block walls and utility penetrations.
Two identical houses next door to each other can test very differently, which is why a neighbor's result tells you nothing definitive about yours.
Testing
A short-term test (2–7 days) in the lowest lived-in level of the home gives you a usable number quickly. Long-term tests (90+ days) give a better annual average.
The EPA recommends fixing homes at or above 4.0 pCi/L and considering action between 2 and 4.
Mitigation
The standard fix is sub-slab depressurization: a sealed suction point under the basement floor, PVC piping routed outside, and an inline fan that vents the gas above the roofline. Most homes are done in a day.
After installation you retest to confirm the number actually dropped — that verification step is the part people skip and shouldn't.
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