Radon Testing & Mitigation in Forest County, PA
49% of 259 basement radon tests reported to PA DEP in Forest County measured 4.0 pCi/L or higher, EPA's action level (median 3.6 pCi/L).
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Radon in Forest County: 49% of the 259 basement tests reported to PA DEP measured 4.0 pCi/L or higher, EPA's action level, 12 points above the 37% statewide share. The sample is small. The county ranks 25th highest of 67, and the median result is 3.6 pCi/L. Only a test shows one home's level.
Radon Test Results by ZIP Code in Forest County
2 ZIP codes in Forest County have at least 20 basement tests on record. The highest share at or above 4.0 pCi/L is in 16239 (Marienville): 54% of 86 tests. The lowest is in 16353 (Tionesta): 48% of 128 tests.
| ZIP code | Post office | Basement tests | Median pCi/L | At or above 4.0 |
|---|---|---|---|---|
| 16353 | Tionesta | 128 | 3.6 | 48% |
| 16239 | Marienville | 86 | 4.7 | 54% |
| Forest County | 259 | 3.6 | 49% | |
| Pennsylvania | 2,629,492 | 2.8 | 37% | |
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Get matched with a DEP-certified radon professionalFirst-floor tests in Forest County: 65 on record, median 1.6 pCi/L, 20% at or above 4.0 pCi/L.
EPA's Map of Radon Zones (1993) places Forest County in Zone 2, its middle category (predicted average between 2 and 4 pCi/L). The map is a county-wide prediction; the figures in this table are measurements.
Figures count tests, not homes. A home tested more than once is counted each time, and tests run after a mitigation system was installed are included because the dataset does not separate them. ZIP codes with fewer than 20 basement tests are not shown.
Housing Age in Forest County
70% of Forest County's 6,937 housing units were built before 1980, 3 points above the 67% statewide figure; 13% date from before 1940. Those homes predate EPA's 1994 model standards for radon-resistant construction. Age does not predict a test result: EPA's guidance is that any home, new or old, may have a radon problem.
Source: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, table B25034. Counts all housing units, including vacant and seasonal ones. Retrieved September 29, 2026.
Bedrock Under Forest County
Pottsville Formation (Pennsylvanian; sandstone and conglomerate) underlies 61% of the county. Shenango Formation through Cuyahoga Group (Mississippian; siltstone and sandstone) underlies 22% of the county.
Mapped bedrock describes an area. The USGS states that its radon assessment cannot be applied to individual homes. More on Pennsylvania radon and geology.
Sources: U.S. Geological Survey State Geologic Map Compilation, from Pennsylvania Geological Survey Map 1 (1980; digital edition 2001). Retrieved September 29, 2026. U.S. Geological Survey Open-File Report 93-292-C, Geologic Radon Potential of EPA Region 3 (1993).
Private Wells in Forest County
An estimated 78% of Forest County residents supplied their own household water in 2015, typically from a private well. Radon dissolves in groundwater and is released into indoor air when water is used for showering and other household purposes. EPA's guidance: if an air test finds a radon problem and your water comes from a well, have the water tested too. A water test is separate from an air test.
Sources: U.S. Geological Survey, Estimated Use of Water in the United States, county-level data for 2015. Retrieved September 29, 2026. U.S. EPA, A Citizen's Guide to Radon.
Home Purchases in Forest County
Lenders reported 32 home-purchase mortgages originated in Forest County in 2024. The count covers financed purchases only; cash purchases are not in the data. See radon in a Pennsylvania home sale.
Source: FFIEC Home Mortgage Disclosure Act data, 2024. Retrieved September 29, 2026.
Municipalities in Forest County
Forest County has 9 municipalities: 1 borough and 8 townships.
Show all 9 municipalities
Barnett township, Green township, Harmony township, Hickory township, Howe township, Jenks township, Kingsley township, Tionesta borough, Tionesta township.
Source: U.S. Census Bureau, 2025 Gazetteer Files, county subdivisions. Retrieved September 29, 2026.
City Pages in Forest County
Neighboring Counties
- Radon in Clarion County → 48% of 3,490 basement tests at or above 4.0 pCi/L
- Radon in Elk County → 48% of 3,490 basement tests at or above 4.0 pCi/L
- Radon in Jefferson County → 56% of 4,552 basement tests at or above 4.0 pCi/L
- Radon in McKean County → 27% of 1,551 basement tests at or above 4.0 pCi/L
- Radon in Venango County → 46% of 4,976 basement tests at or above 4.0 pCi/L
- Radon in Warren County → 48% of 3,839 basement tests at or above 4.0 pCi/L
- All 67 Pennsylvania county radon pages
DEP-Certified Mitigation Firms Based in County
No DEP-certified mitigation firms are physically based in Forest County. Certified professionals from adjacent counties travel here to perform testing and mitigation.
Source: PA DEP Certified Mitigation Firms Directory, July 2026. This reflects business address only — firms based elsewhere may also serve Forest County.
Testing, Cost and Certification
Short-term tests run 48–96 hours; long-term tests run 90 days or more. At 4.0 pCi/L or higher, retest or mitigate. How radon testing works in a Pennsylvania real estate transaction.
Mitigation in Forest County typically costs $950–$2,050. Pennsylvania radon mitigation cost guide.
Anyone testing or mitigating for pay must hold DEP certification under 25 Pa. Code § 240. How to verify a contractor in the PA DEP Radon Services Directory.
Frequently Asked Questions
What share of radon tests in Forest County are at or above the EPA action level?
49% of the 259 basement tests reported to PA DEP from Forest County measured 4.0 pCi/L or higher, against 37% statewide. The median result is 3.6 pCi/L, and 14% of tests measured 20 pCi/L or higher.
Which Forest County ZIP code has the highest radon test results?
Among ZIP codes with at least 20 basement tests, 16239 (Marienville) has the highest share at or above 4.0 pCi/L: 54% of 86 tests, with a median of 4.7 pCi/L. 16353 (Tionesta) has the lowest, at 48%.
How does Forest County compare with other Pennsylvania counties?
Forest County ranks 25th highest of 67 counties by share of basement tests at or above 4.0 pCi/L, at 49%. Among its neighbors, Jefferson County has the highest share at 56% and McKean County the lowest at 27%.
What bedrock is under Forest County?
The largest mapped units are Pottsville Formation (61% of the county) and Shenango Formation through Cuyahoga Group (22% of the county), according to the USGS compilation of the Pennsylvania Geological Survey state map.
Should Forest County well owners test their water for radon?
An estimated 78% of Forest County residents supplied their own household water in 2015. EPA's guidance is to test the air first. If the air test finds a radon problem and the water comes from a well, have the water tested as well.