Radon Testing & Mitigation in Blair County, PA
43% of 17,286 basement radon tests reported to PA DEP in Blair County measured 4.0 pCi/L or higher, EPA's action level (median 3.2 pCi/L).
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Radon in Blair County: 43% of the 17,286 basement tests reported to PA DEP measured 4.0 pCi/L or higher, EPA's action level, 6 points above the 37% statewide share. The county ranks 44th highest of 67, and the median result is 3.2 pCi/L. Only a test shows one home's level.
Radon Test Results by ZIP Code in Blair County
12 ZIP codes in Blair County have at least 20 basement tests on record. Among those with 100 or more, the highest share at or above 4.0 pCi/L is in 16673 (Roaring Spring): 70% of 535 tests. The lowest is in 16601 (Altoona): 33% of 3,198 tests.
| ZIP code | Post office | Basement tests | Median pCi/L | At or above 4.0 |
|---|---|---|---|---|
| 16648 | Hollidaysburg | 4,454 | 3.0 | 40% |
| 16602 | Altoona | 4,260 | 3.4 | 45% |
| 16601 | Altoona | 3,198 | 2.4 | 33% |
| 16635 | Duncansville | 2,426 | 3.3 | 43% |
| 16686 | Tyrone | 1,073 | 3.7 | 48% |
| 16662 | Martinsburg | 553 | 7.3 | 67% |
| 16673 | Roaring Spring | 535 | 7.3 | 70% |
| 16617 | Bellwood | 252 | 3.2 | 38% |
| 16693 | Williamsburg | 247 | 5.1 | 60% |
| 16637 | East Freedom | 100 | 4.4 | 51% |
| 16625 | Claysburg | 81 | 3.0 | 47% |
| 16665 | Newry | 32 | 2.7 | 22% |
| Blair County | 17,286 | 3.2 | 43% | |
| Pennsylvania | 2,629,492 | 2.8 | 37% | |
See your ZIP in the table?
Get matched with a DEP-certified radon professionalFirst-floor tests in Blair County: 1,380 on record, median 1.7 pCi/L, 23% at or above 4.0 pCi/L.
EPA's Map of Radon Zones (1993) places Blair County in Zone 1, its highest category (predicted average indoor screening level above 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 Blair County
75% of Blair County's 55,901 housing units were built before 1980, 8 points above the 67% statewide figure; 31% 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 Blair County
Brallier and Harrell Formations (Devonian; siltstone and shale) underlies 9% of the county. Catskill Formation (Devonian; siltstone, shale and sandstone) underlies 7% of the county. Bellefonte and Axemann Formations (Ordovician; dolomite and limestone) underlies 7% of the county. No single unit covers more than 9% of the county.
Limestone and dolomite are usually low in uranium themselves, but the soils left behind as the rock dissolves are often enriched in uranium and radium, and solution cavities in the rock give soil gas extra pathways.
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).
Home Purchases in Blair County
Lenders reported 923 home-purchase mortgages originated in Blair 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 Blair County
Blair County has 25 municipalities: 1 city, 9 boroughs and 15 townships.
Show all 25 municipalities
Allegheny township, Altoona city, Antis township, Bellwood borough, Blair township, Catharine township, Duncansville borough, Frankstown township, Freedom township, Greenfield township, Hollidaysburg borough, Huston township, Juniata township, Logan township, Martinsburg borough, Newry borough, North Woodbury township, Roaring Spring borough, Snyder township, Taylor township, Tunnelhill borough, Tyrone borough, Tyrone township, Williamsburg borough, Woodbury township.
Source: U.S. Census Bureau, 2025 Gazetteer Files, county subdivisions. Retrieved September 29, 2026.
City Pages in Blair County
Neighboring Counties
- Radon in Bedford County → 55% of 4,032 basement tests at or above 4.0 pCi/L
- Radon in Cambria County → 44% of 16,280 basement tests at or above 4.0 pCi/L
- Radon in Centre County → 56% of 39,672 basement tests at or above 4.0 pCi/L
- Radon in Clearfield County → 53% of 10,770 basement tests at or above 4.0 pCi/L
- Radon in Huntingdon County → 53% of 3,957 basement tests at or above 4.0 pCi/L
- All 67 Pennsylvania county radon pages
DEP-Certified Mitigation Firms Based in County
1 DEP-certified mitigation firm is physically based in Blair County. Firms from adjacent counties routinely serve here as well.
Source: PA DEP Certified Mitigation Firms Directory, July 2026. This reflects business address only — firms based elsewhere may also serve Blair 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 Blair County typically costs $875–$2,350. 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 Blair County are at or above the EPA action level?
43% of the 17,286 basement tests reported to PA DEP from Blair County measured 4.0 pCi/L or higher, against 37% statewide. The median result is 3.2 pCi/L, and 6% of tests measured 20 pCi/L or higher.
Which Blair County ZIP code has the highest radon test results?
Among ZIP codes with at least 100 basement tests, 16673 (Roaring Spring) has the highest share at or above 4.0 pCi/L: 70% of 535 tests, with a median of 7.3 pCi/L. 16601 (Altoona) has the lowest, at 33%.
How does Blair County compare with other Pennsylvania counties?
Blair County ranks 44th highest of 67 counties by share of basement tests at or above 4.0 pCi/L, at 43%. Among its neighbors, Centre County has the highest share at 56% and Cambria County the lowest at 44%.
What bedrock is under Blair County?
The largest mapped units are Brallier and Harrell Formations (9% of the county), Catskill Formation (7% of the county) and Bellefonte and Axemann Formations (7% of the county), according to the USGS compilation of the Pennsylvania Geological Survey state map.