Updated November 2026 · Data: Pennsylvania DEP radon test and mitigation databases · Sources and method
Pennsylvania DEP has records of 11,841 radon tests in homes with a Johnstown, PA mailing address. Of those, 41.9% were at or above the EPA action level of 4 pCi/L, and the median result was 3.4 pCi/L. That share is close to the Cambria County figure of 41.8% (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 Johnstown
ZIP codes used in Johnstown mailing addresses, with at least 50 tests.
| ZIP code | Tests | Median (pCi/L) | At or above 4 pCi/L |
|---|---|---|---|
| 15901 | 146 | 2.1 | 32.2% |
| 15902 | 920 | 2.8 | 36.0% |
| 15904 | 3,787 | 3.4 | 41.5% |
| 15905 | 5,790 | 3.5 | 43.8% |
| 15906 | 708 | 2.6 | 29.9% |
| 15909 | 435 | 4.6 | 54.5% |
Highest shares of high results (200+ tests): 15909 (54.5%), 15905 (43.8%), 15904 (41.5%).
Results by floor
| Floor tested | Tests | Median (pCi/L) | At or above 4 pCi/L |
|---|---|---|---|
| Basement | 10,284 | 3.5 | 43.4% |
| Slab On Grade | 693 | 3.3 | 40.4% |
| First Floor | 566 | 1.9 | 24.7% |
| Second Floor | 85 | 1.8 | 25.9% |
| Crawl Space | 37 | 2.2 | 16.2% |
Recent tests (2016 to 2026)
Of the 3,290 tests since 2016, 40.2% were at or above 4 pCi/L and the median was 3.3 pCi/L.
Radon mitigation in Johnstown
- The median reported cost of 78 mitigation systems installed in Johnstown from 2022 to 2026 was $1,800 (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 Cambria County · Radon in Pennsylvania.
Frequently asked questions
Is radon a problem in Johnstown, PA?
41.9% of 11,841 radon tests in Johnstown 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 Johnstown?
The median of all PA DEP test results for Johnstown mailing addresses is 3.4 pCi/L. We use the median because a few very high readings would distort a simple average.
How much does radon mitigation cost in Johnstown?
The median reported cost of 78 systems installed from 2022 to 2026 was $1,800, 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 Johnstown. 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.