Radon Testing & Mitigation in Dauphin County, PA
53% of 64,393 basement radon tests reported to PA DEP in Dauphin County measured 4.0 pCi/L or higher, EPA's action level (median 4.4 pCi/L).
Connect with a DEP-Certified Radon Professional
or call(717) 461-2427
Radon in Dauphin County: 53% of the 64,393 basement tests reported to PA DEP measured 4.0 pCi/L or higher, EPA's action level, 16 points above the 37% statewide share. The county ranks 18th highest of 67, and the median result is 4.4 pCi/L. Only a test shows one home's level.
Radon Test Results by ZIP Code in Dauphin County
26 ZIP codes in Dauphin 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 17032 (Halifax): 69% of 1,731 tests. The lowest is in 17102 (Harrisburg): 21% of 1,028 tests.
| ZIP code | Post office | Basement tests | Median pCi/L | At or above 4.0 |
|---|---|---|---|---|
| 17112 | Harrisburg | 12,548 | 4.6 | 54% |
| 17111 | Harrisburg | 10,198 | 5.7 | 58% |
| 17036 | Hummelstown | 9,993 | 4.7 | 54% |
| 17110 | Harrisburg | 6,362 | 3.0 | 41% |
| 17033 | Hershey | 6,350 | 4.1 | 51% |
| 17109 | Harrisburg | 5,351 | 5.9 | 62% |
| 17057 | Middletown | 3,139 | 2.8 | 38% |
| 17032 | Halifax | 1,731 | 10.0 | 69% |
| 17113 | Harrisburg | 1,346 | 6.6 | 63% |
| 17104 | Harrisburg | 1,280 | 3.1 | 45% |
| 17102 | Harrisburg | 1,028 | 1.4 | 21% |
| 17061 | Millersburg | 908 | 6.4 | 63% |
| 17018 | Dauphin | 904 | 5.6 | 60% |
| 17103 | Harrisburg | 696 | 3.0 | 42% |
| 17028 | Grantville (part) | 486 | 5.3 | 57% |
Show all 26 ZIP codes
| 17023 | Elizabethville | 469 | 5.2 | 60% |
| 17034 | Highspire | 317 | 2.5 | 31% |
| 17048 | Lykens | 273 | 4.0 | 50% |
| 17101 | Harrisburg | 256 | 1.7 | 27% |
| 17022 | Elizabethtown (part) | 196 | 4.0 | 51% |
| 17098 | Williamstown | 160 | 3.9 | 49% |
| 17078 | Palmyra (part) | 105 | 2.4 | 40% |
| 17030 | Gratz | 83 | 6.1 | 58% |
| 17120 | Harrisburg | 42 | 1.6 | 12% |
| 17105 | Harrisburg | 39 | 2.3 | 36% |
| 17097 | Wiconsico | 26 | 2.6 | 31% |
| Dauphin County | 64,393 | 4.4 | 53% | |
| Pennsylvania | 2,629,492 | 2.8 | 37% | |
See your ZIP in the table?
Get matched with a DEP-certified radon professionalFirst-floor tests in Dauphin County: 13,913 on record, median 1.9 pCi/L, 31% at or above 4.0 pCi/L.
EPA's Map of Radon Zones (1993) places Dauphin 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 Dauphin County
62% of Dauphin County's 127,828 housing units were built before 1980, 5 points below the 67% statewide figure; 19% 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 Dauphin County
Mauch Chunk Formation (Mississippian; siltstone, shale and sandstone) underlies 24% of the county. Catskill Formation, including its mapped members (Devonian; siltstone and mudstone) underlies 19% of the county. Hamburg sequence rocks (Ordovician; shale) underlies 15% 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).
Home Purchases in Dauphin County
Lenders reported 3,059 home-purchase mortgages originated in Dauphin 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 Dauphin County
Dauphin County has 40 municipalities: 1 city, 16 boroughs and 23 townships.
Show all 40 municipalities
Berrysburg borough, Conewago township, Dauphin borough, Derry township, East Hanover township, Elizabethville borough, Gratz borough, Halifax borough, Halifax township, Harrisburg city, Highspire borough, Hummelstown borough, Jackson township, Jefferson township, Londonderry township, Lower Paxton township, Lower Swatara township, Lykens borough, Lykens township, Middle Paxton township, Middletown borough, Mifflin township, Millersburg borough, Paxtang borough, Penbrook borough, Pillow borough, Reed township, Royalton borough, Rush township, South Hanover township, Steelton borough, Susquehanna township, Swatara township, Upper Paxton township, Washington township, Wayne township, West Hanover township, Wiconisco township, Williams township, Williamstown borough.
Source: U.S. Census Bureau, 2025 Gazetteer Files, county subdivisions. Retrieved September 29, 2026.
City Pages in Dauphin County
Neighboring Counties
- Radon in Cumberland County → 55% of 76,003 basement tests at or above 4.0 pCi/L
- Radon in Juniata County → 62% of 1,798 basement tests at or above 4.0 pCi/L
- Radon in Lancaster County → 55% of 109,065 basement tests at or above 4.0 pCi/L
- Radon in Lebanon County → 60% of 26,666 basement tests at or above 4.0 pCi/L
- Radon in Northumberland County → 47% of 9,978 basement tests at or above 4.0 pCi/L
- Radon in Perry County → 62% of 5,945 basement tests at or above 4.0 pCi/L
- Radon in Schuylkill County → 56% of 18,595 basement tests at or above 4.0 pCi/L
- Radon in York County → 57% of 81,620 basement tests at or above 4.0 pCi/L
- All 67 Pennsylvania county radon pages
DEP-Certified Mitigation Firms Based in County
5 DEP-certified mitigation firms are physically based in Dauphin 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 Dauphin 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 Dauphin County typically costs $900–$2,300. 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 Dauphin County are at or above the EPA action level?
53% of the 64,393 basement tests reported to PA DEP from Dauphin County measured 4.0 pCi/L or higher, against 37% statewide. The median result is 4.4 pCi/L, and 14% of tests measured 20 pCi/L or higher.
Which Dauphin County ZIP code has the highest radon test results?
Among ZIP codes with at least 100 basement tests, 17032 (Halifax) has the highest share at or above 4.0 pCi/L: 69% of 1,731 tests, with a median of 10.0 pCi/L. 17102 (Harrisburg) has the lowest, at 21%.
How does Dauphin County compare with other Pennsylvania counties?
Dauphin County ranks 18th highest of 67 counties by share of basement tests at or above 4.0 pCi/L, at 53%. Among its neighbors, Juniata County has the highest share at 62% and Northumberland County the lowest at 47%.
What bedrock is under Dauphin County?
The largest mapped units are Mauch Chunk Formation (24% of the county), Catskill Formation (19% of the county) and Hamburg sequence rocks (15% of the county), according to the USGS compilation of the Pennsylvania Geological Survey state map.