Radon in Indiana: radon map by county
EPA's Map of Radon Zones puts 57 of Indiana's 92 counties in Zone 1 (predicted average indoor radon above 4 pCi/L), 35 in Zone 2 and 0 in Zone 3. Of 36,725 building tests that radon laboratories reported for 2008 to 2017, 38.6% were at or above EPA's 4 pCi/L action level, against 36.5% nationally (number 16 of 42 states with 1,000+ tests). The highest county share is Parke County (68% of 20 tests).
Radon by county in Indiana
| County | EPA zone | Lab tests | Median | 4+ pCi/L |
|---|---|---|---|---|
| Adams County | Zone 1 | 62 | 3.8 | 48.5% |
| Allen County | Zone 1 | 3,264 | 3.3 | 41.8% |
| Bartholomew County | Zone 1 | 1,229 | 3.9 | 48.7% |
| Benton County | Zone 1 | 29 | 5.7 | 61.8% |
| Blackford County | Zone 1 | 9 | 3.6 | 36.4% |
| Boone County | Zone 1 | 476 | 3.0 | 39.7% |
| Brown County | Zone 2 | 96 | 2.8 | 25.9% |
| Carroll County | Zone 1 | 31 | 5.8 | 60.5% |
| Cass County | Zone 1 | 85 | 2.6 | 34.1% |
| Clark County | Zone 1 | 381 | 3.6 | 47.7% |
| Clay County | Zone 2 | 19 | 2.9 | 26.1% |
| Clinton County | Zone 1 | 65 | 3.5 | 45.9% |
| Crawford County | Zone 2 | 8 | 2.7 | 30% |
| Daviess County | Zone 2 | 47 | 3.1 | 34.5% |
| Dearborn County | Zone 2 | 122 | 2.6 | 30.1% |
| Decatur County | Zone 1 | 54 | 2.8 | 33.3% |
| DeKalb County | Zone 1 | 216 | 4.4 | 56.6% |
| Delaware County | Zone 1 | 143 | 4.2 | 55.1% |
| Dubois County | Zone 2 | 107 | 3.7 | 44.1% |
| Elkhart County | Zone 1 | 2,636 | 3.7 | 46.4% |
| Fayette County | Zone 1 | 12 | 7.9 | 76.9% |
| Floyd County | Zone 2 | 241 | 3.3 | 42.4% |
| Fountain County | Zone 1 | 38 | 4.6 | 55% |
| Franklin County | Zone 2 | 52 | 2.1 | 28% |
| Fulton County | Zone 1 | 88 | 3.3 | 46.4% |
| Gibson County | Zone 2 | 107 | 3.4 | 43.3% |
| Grant County | Zone 1 | 69 | 4.6 | 58.2% |
| Greene County | Zone 2 | 36 | 3.0 | 32.7% |
| Hamilton County | Zone 1 | 2,787 | 2.7 | 37.6% |
| Hancock County | Zone 1 | 235 | 2.6 | 33.9% |
| Harrison County | Zone 1 | 141 | 5.5 | 62.4% |
| Hendricks County | Zone 1 | 964 | 3.2 | 41.5% |
| Henry County | Zone 1 | 80 | 4.0 | 50.5% |
| Howard County | Zone 1 | 156 | 3.8 | 49.1% |
| Huntington County | Zone 1 | 147 | 3.5 | 43.8% |
| Jackson County | Zone 2 | 74 | 2.8 | 27.3% |
| Jasper County | Zone 2 | 62 | 1.2 | 14.1% |
| Jay County | Zone 1 | 8 | 2.7 | 44.4% |
| Jefferson County | Zone 2 | 51 | 3.1 | 45.8% |
| Jennings County | Zone 1 | 51 | 2.8 | 35.1% |
| Johnson County | Zone 1 | 469 | 2.9 | 39.4% |
| Knox County | Zone 2 | 45 | 3.4 | 43.1% |
| Kosciusko County | Zone 1 | 1,192 | 4.0 | 50.6% |
| LaGrange County | Zone 1 | 114 | 3.4 | 41.7% |
| Lake County | Zone 2 | 1,092 | 1.8 | 23.5% |
| LaPorte County | Zone 2 | 625 | 5.0 | 58.2% |
| Lawrence County | Zone 1 | 177 | 2.7 | 35.6% |
| Madison County | Zone 1 | 208 | 3.8 | 49% |
| Marion County | Zone 1 | 2,993 | 3.1 | 40.1% |
| Marshall County | Zone 1 | 334 | 3.2 | 39.7% |
| Martin County | Zone 2 | 6 | 3.7 | 37.5% |
| Miami County | Zone 1 | 25 | 5.3 | 63.3% |
| Monroe County | Zone 1 | 1,731 | 2.8 | 34.2% |
| Montgomery County | Zone 1 | 104 | 2.9 | 41.4% |
| Morgan County | Zone 2 | 213 | 3.5 | 44.2% |
| Newton County | Zone 2 | 15 | 1.6 | 12.5% |
| Noble County | Zone 1 | 120 | 4.3 | 52.9% |
| Ohio County | Zone 2 | 18 | 4.1 | 52.4% |
| Orange County | Zone 1 | 13 | 2.9 | 43.5% |
| Owen County | Zone 2 | 83 | 2.8 | 39.1% |
| Parke County | Zone 2 | 20 | 4.8 | 68% |
| Perry County | Zone 2 | 19 | 2.3 | 23.1% |
| Pike County | Zone 2 | 7 | 3.6 | 50% |
| Porter County | Zone 2 | 988 | 3.5 | 46.5% |
| Posey County | Zone 2 | 190 | 2.8 | 35.3% |
| Pulaski County | Zone 2 | 16 | 2.3 | 31.8% |
| Putnam County | Zone 1 | 79 | 2.7 | 34.5% |
| Randolph County | Zone 1 | 25 | 4.5 | 60.7% |
| Ripley County | Zone 2 | 65 | 2.9 | 35.3% |
| Rush County | Zone 1 | 12 | 3.9 | 47.1% |
| Scott County | Zone 1 | 11 | 2.0 | 35.3% |
| Shelby County | Zone 1 | 68 | 4.0 | 50% |
| Spencer County | Zone 2 | 22 | 4.5 | 60% |
| St. Joseph County | Zone 1 | 7,007 | 2.7 | 29.3% |
| Starke County | Zone 2 | 24 | 1.6 | 4.2% |
| Steuben County | Zone 1 | 125 | 4.5 | 55.7% |
| Sullivan County | Zone 2 | 11 | 3.1 | 46.2% |
| Switzerland County | Zone 2 | 9 | 1.5 | 33.3% |
| Tippecanoe County | Zone 1 | 968 | 2.7 | 36.8% |
| Tipton County | Zone 1 | 53 | 3.9 | 49.3% |
| Union County | Zone 1 | 7 | 3.8 | 50% |
| Vanderburgh County | Zone 2 | 1,387 | 2.4 | 24.4% |
| Vermillion County | Zone 1 | 17 | 3.3 | 41.7% |
| Vigo County | Zone 2 | 399 | 3.6 | 44% |
| Wabash County | Zone 1 | 83 | 5.8 | 59.3% |
| Warren County | Zone 1 | 25 | 3.5 | 33.3% |
| Warrick County | Zone 2 | 539 | 1.8 | 20.9% |
| Washington County | Zone 1 | 29 | 3.5 | 42.1% |
| Wayne County | Zone 1 | 132 | 4.5 | 56.4% |
| Wells County | Zone 1 | 112 | 3.6 | 47.8% |
| White County | Zone 1 | 32 | 2.7 | 35.7% |
| Whitley County | Zone 1 | 189 | 4.0 | 51.6% |
Lab tests: buildings tested by radon laboratories, 2008 to 2017; median in pCi/L; “4+ pCi/L” is the share of tests at or above EPA's action level. n/a: no value on file (no tests, or too few to report).
What the zones mean
Zone 1 counties have a predicted average indoor radon screening level above 4 pCi/L, Zone 2 from 2 to 4 pCi/L and Zone 3 below 2 pCi/L. The prediction is from 1993 indoor measurements, geology, aerial radioactivity, soils and foundation types. EPA: “This map should not be used to determine if individual homes need to be tested.” EPA recommends fixing a home at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of exposure.
Radon in Indiana: questions
What radon zone is Indiana?
EPA's 1993 map does not give states one zone; it zones each county. In Indiana, 57 counties are Zone 1, 35 Zone 2 and 0 Zone 3. EPA says the map "should not be used to determine if individual homes need to be tested".
Which Indiana counties have the highest radon levels?
By the share of laboratory tests at or above 4 pCi/L for 2008 to 2017 (counties with 20 or more tests): Parke County 68% (median 4.8 pCi/L, 20 tests); Miami County 63.3% (median 5.3 pCi/L, 25 tests); Harrison County 62.4% (median 5.5 pCi/L, 141 tests); Benton County 61.8% (median 5.7 pCi/L, 29 tests); Randolph County 60.7% (median 4.5 pCi/L, 25 tests).
How common is high radon in Indiana?
38.6% of the 36,725 tests in the laboratory data for Indiana (2008 to 2017) were at or above 4 pCi/L; the national share was 36.5%. Buildings are tested by choice, often because of a sale or a concern, so the share describes the tests on file, not every home.
Should I test for radon in Indiana?
Yes. EPA recommends testing every home no matter where it is, fixing it at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of radon exposure.
States bordering Indiana
Other free hazard lookups
- Radon by county and ZIP codeEPA radon zone and the radon test results on file for any county, ZIP code or address.
- Fault lines near an addressUSGS-mapped earthquake faults within 5 miles, their age and slip rate, and the USGS seismic hazard value.
- Power lines near an addressHigh-voltage transmission lines within 1 mile from federal maps, with voltage and distance.
- Flood zone lookupThe FEMA flood zone mapped at any US address. Not an official flood zone determination.
- Superfund sites near an addressThe nearest EPA Superfund (NPL) sites and their status.
All of these, plus wetlands, FEMA hazard ratings and the federal contamination lists, are in the Environmental Records Report for any US address ($29).
Superfund sites in Indiana · Radon map of every state
Data compiled 2026-10-20. County-level screening information, not a radon measurement of any building.