Updated November 2026 · Data: Pennsylvania DEP radon test and mitigation databases · Sources and method
Pennsylvania DEP has records of 8,131 radon tests in homes with a Williamsport, PA mailing address. Of those, 35.6% were at or above the EPA action level of 4 pCi/L, and the median result was 2.6 pCi/L. That share is lower than the Lycoming County figure of 42.2% (Pennsylvania: 33.9%).
These are area results, not your home’s level. Homes on the same street can have very different radon levels. The only way to know yours is to test.
Radon by ZIP code in Williamsport
ZIP codes used in Williamsport mailing addresses, with at least 50 tests.
| ZIP code | Tests | Median (pCi/L) | At or above 4 pCi/L |
|---|---|---|---|
| 17701 | 7,447 | 2.5 | 35.1% |
| 17702 | 672 | 3.1 | 40.9% |
Highest shares of high results (200+ tests): 17702 (40.9%), 17701 (35.1%).
Results by floor
| Floor tested | Tests | Median (pCi/L) | At or above 4 pCi/L |
|---|---|---|---|
| Basement | 6,648 | 3.0 | 39.2% |
| First Floor | 1,228 | 1.4 | 16.9% |
| Slab On Grade | 62 | 3.4 | 43.5% |
| Second Floor | 40 | 0.7 | 20.0% |
Recent tests (2016 to 2026)
Of the 2,914 tests since 2016, 30.6% were at or above 4 pCi/L and the median was 2.2 pCi/L.
Radon mitigation in Williamsport
- The median reported cost of 94 mitigation systems installed in Williamsport from 2022 to 2026 was $1,480 (PA DEP mitigation records).
- Pennsylvania requires radon testers and mitigators to be certified by DEP. Find one in the DEP radon services directory or call 1-800-23-RADON.
- Compare prices in our radon mitigation cost guide.
How to test your home
- Short-term kits cost about $20 to $30 at hardware stores and from Pennsylvania-certified labs (PA DEP).
- Test the lowest lived-in level of the home with windows and doors closed.
- If the result is 4 pCi/L or higher, the EPA recommends fixing the home; between 2 and 4 pCi/L, consider a fix.
More results nearby: Radon in Lycoming County · Radon in Pennsylvania.
Frequently asked questions
Is radon a problem in Williamsport, PA?
35.6% of 8,131 radon tests in Williamsport homes recorded by PA DEP were at or above 4 pCi/L. Any home can have high radon, so testing is the only way to know.
What is the average radon level in Williamsport?
The median of all PA DEP test results for Williamsport mailing addresses is 2.6 pCi/L. We use the median because a few very high readings would distort a simple average.
How much does radon mitigation cost in Williamsport?
The median reported cost of 94 systems installed from 2022 to 2026 was $1,480, according to PA DEP records.
Sources and method
Statistics use the Pennsylvania DEP radon test database (about 3.4 million tests from 1986 to October 2026), limited to residential and unspecified buildings, for homes whose mailing address city is Williamsport. A mailing city can cover several municipalities and ZIP codes. Records can include repeat tests of the same home and some tests after mitigation. Data retrieved November 2026.