Borough, York County

Radon Mitigation in Jefferson, PA

Updated September 30, 2026

Jefferson is a borough in York County with about 437 residents and 189 homes, median year built 1962. It is nearly encircled by Codorus Township. The borough was incorporated in 1866 and named for Thomas Jefferson. 58.6% of PA DEP radon tests in its ZIP codes came back at or above the action level, above the county's 52.5%.

What the PA DEP test records show for Jefferson

ZIP 17362 covers 92% of Jefferson's land, so these numbers are about as local as public radon data gets.

Look past the median to the high end. One test in 4 here came in at 20 pCi/L or more, five times the action level, and the highest reading on record is 673 pCi/L. Neighboring houses can differ by a factor of ten, so none of this tells you what your house is. It tells you the odds are high enough that a $15 to $30 test kit is worth buying.

Tests people chose to run, not a random survey. Details on the York County radon levels page.

Basement readings versus first-floor readings

In ZIP 17362, basement tests have a median of 7.2 pCi/L, while tests taken on the first floor have a median of 2.8 pCi/L (276 first-floor tests). The basement number runs 2.6 times the first-floor number, which is the usual pattern: radon comes up from the soil, so it is strongest at the lowest level and gets diluted as it moves up through the house.

It also explains why two neighbors can get very different results. One tested a finished basement, the other tested a first-floor bedroom. For a decision about mitigation, the test that counts is the one from the lowest level anyone spends time in.

Radon results by decade in ZIP 17362

The share peaked in the 2010s at 62.2% and sits at 56.1% for tests since 2020. That is a small move, well within what you'd expect from a shifting mix of home-sale tests and retests. 578 tests have been logged in 17362 since 2020, so people here are still testing.

Housing in Jefferson and what it means for a system

Census Bureau, American Community Survey 2020 to 2024:

41.3% of the homes in Jefferson were built before 1940, against 18.3% county-wide. Houses that old usually sit on stone or early block foundations with no vapor barrier and plenty of joints, which gives soil gas more ways in. They are still very fixable. The installer just spends more time sealing, and sometimes needs a second suction point, which is why these jobs tend to land toward the upper end of the cost range.

78.8% of homes in Jefferson are single-family detached. A detached house with a basement is the easiest layout to mitigate: one suction point through the slab, a fan outside or in the garage, and a vent above the roof line. It is the standard sub-slab depressurization job covered step by step on our mitigation process page, and it usually lands in the middle of the cost range.

Cost-wise, expect older houses in Jefferson to land in the $1,200 to $2,500 part of the range once sealing and a possible second suction point are counted. Newer houses are usually the standard $800 to $1,500 job. Full ranges on the cost page.

Where we work in Jefferson

The borough was incorporated in 1866 and named for Thomas Jefferson.

Installers must hold a PA DEP radon mitigation certification (how to check), and permit questions go to the borough office at www.jeffersonboro.net.

Common questions

Is radon a problem in Jefferson?

Yes. PA DEP has 3,003 tests on record from the ZIP code covering Jefferson, and 58.6% of them came back at or above the EPA's 4.0 pCi/L action level. 22.9% were at 20 pCi/L or more. The county-wide rate is 52.5%.

What is the average radon level in ZIP 17362?

The median of 3,003 PA DEP tests in ZIP 17362 is 5.8 pCi/L and the mean is 17.5 pCi/L. A mean that far above the median means a long tail of very high readings, topping out at 673 pCi/L.

Nearby

Spring Grove 58.6%, North Codorus Township 55.6%, Jackson Township 53.7%, Heidelberg Township 49.4%, Codorus Township 59.6%. Share of PA DEP tests at or above 4.0 pCi/L, against 58.6% here.