Updated November 2026 · Data: Pennsylvania DEP radon test and mitigation databases, EPA Map of Radon Zones · Sources and method
Pennsylvania DEP has records of 389,643 radon tests in Montgomery County homes. Of those, 24.6% were at or above the EPA action level of 4 pCi/L, and the median result was 2.1 pCi/L. That share is lower than the Pennsylvania figure of 33.9%. Montgomery County is in EPA radon Zone 1 (highest potential). Below are results by ZIP code and community, by floor of the home, and what radon mitigation has cost in the county.
These are area results, not your home’s level. Homes next to each other can have very different radon levels. The only way to know yours is to test.
Radon test results by ZIP code in Montgomery County
ZIP codes with at least 20 tests on record. “At or above 4 pCi/L” is the share of tests at or above the EPA action level.
| ZIP code | Tests | Median (pCi/L) | At or above 4 pCi/L |
|---|---|---|---|
| 18041 | 1,195 | 2.5 | 32.3% |
| 18054 | 1,215 | 2.6 | 33.8% |
| 18070 | 160 | 3.6 | 46.9% |
| 18073 | 2,885 | 2.8 | 34.7% |
| 18074 | 1,828 | 2.1 | 24.2% |
| 18076 | 683 | 2.1 | 24.6% |
| 18084 | 55 | 1.7 | 27.3% |
| 18901 | 120 | 1.8 | 25.0% |
| 18914 | 111 | 2.6 | 33.3% |
| 18915 | 521 | 2.3 | 24.4% |
| 18924 | 40 | 2.3 | 27.5% |
| 18936 | 510 | 1.7 | 19.8% |
| 18944 | 90 | 1.6 | 13.3% |
| 18957 | 46 | 4.3 | 54.3% |
| 18964 | 4,547 | 2.2 | 24.9% |
| 18969 | 3,733 | 2.2 | 25.2% |
| 18979 | 20 | 3.6 | 40.0% |
| 19000 | 23 | 1.6 | 8.7% |
| 19001 | 8,453 | 2.1 | 19.3% |
| 19002 | 20,674 | 2.2 | 25.4% |
| 19003 | 3,625 | 1.7 | 15.0% |
| 19004 | 6,319 | 2.5 | 29.3% |
| 19006 | 10,489 | 2.4 | 28.3% |
| 19009 | 299 | 2.9 | 41.5% |
| 19010 | 5,636 | 2.0 | 19.8% |
| 19012 | 3,605 | 2.3 | 20.3% |
| 19025 | 3,879 | 2.1 | 21.0% |
| 19027 | 7,579 | 2.4 | 28.9% |
| 19031 | 2,886 | 2.8 | 32.9% |
| 19034 | 4,190 | 2.2 | 22.3% |
| 19035 | 3,626 | 2.5 | 30.8% |
| 19038 | 15,600 | 2.3 | 24.4% |
| 19040 | 7,329 | 2.1 | 21.4% |
| 19041 | 2,647 | 2.3 | 24.2% |
| 19044 | 6,908 | 1.8 | 19.9% |
| 19046 | 9,672 | 3.0 | 36.7% |
| 19047 | 43 | 2.6 | 18.6% |
| 19066 | 4,038 | 2.5 | 30.2% |
| 19072 | 7,026 | 2.6 | 31.1% |
| 19075 | 4,420 | 2.8 | 30.5% |
| 19083 | 44 | 1.1 | 6.8% |
| 19085 | 1,849 | 1.7 | 12.6% |
| 19087 | 2,781 | 2.7 | 37.9% |
| 19090 | 6,742 | 1.7 | 10.2% |
| 19095 | 3,119 | 2.7 | 33.0% |
| 19096 | 9,458 | 2.3 | 22.7% |
| 19111 | 150 | 2.8 | 29.3% |
| 19118 | 955 | 2.3 | 25.1% |
| 19126 | 161 | 2.4 | 19.3% |
| 19151 | 20 | 1.1 | 15.0% |
| 19301 | 90 | 2.3 | 34.4% |
| 19401 | 10,823 | 1.6 | 14.5% |
| 19403 | 21,422 | 2.0 | 26.2% |
| 19404 | 169 | 1.4 | 16.6% |
| 19405 | 1,683 | 2.0 | 18.7% |
| 19406 | 10,070 | 1.8 | 19.3% |
| 19407 | 469 | 2.5 | 38.0% |
| 19408 | 142 | 2.7 | 40.1% |
| 19409 | 46 | 2.9 | 41.3% |
| 19420 | 48 | 2.5 | 35.4% |
| 19422 | 12,640 | 2.1 | 23.5% |
| 19423 | 39 | 2.0 | 20.5% |
| 19424 | 20 | 2.5 | 30.0% |
| 19426 | 21,830 | 2.0 | 26.2% |
| 19428 | 9,471 | 2.2 | 24.7% |
| 19430 | 32 | 1.8 | 34.4% |
| 19435 | 74 | 3.4 | 33.8% |
| 19436 | 284 | 2.3 | 25.7% |
| 19437 | 836 | 3.0 | 37.6% |
| 19438 | 11,063 | 2.1 | 24.9% |
| 19440 | 6,177 | 2.0 | 20.3% |
| 19441 | 23 | 1.4 | 13.0% |
| 19442 | 44 | 2.0 | 22.7% |
| 19443 | 53 | 2.1 | 15.1% |
| 19444 | 6,364 | 2.2 | 21.8% |
| 19446 | 26,448 | 1.9 | 20.7% |
| 19450 | 142 | 2.7 | 31.0% |
| 19451 | 24 | 3.0 | 33.3% |
| 19452 | 50 | 2.2 | 26.0% |
| 19453 | 400 | 2.5 | 33.0% |
| 19454 | 13,883 | 2.1 | 23.3% |
| 19456 | 284 | 2.3 | 22.2% |
| 19460 | 2,833 | 2.3 | 30.0% |
| 19462 | 5,623 | 1.9 | 20.6% |
| 19464 | 15,105 | 2.3 | 27.6% |
| 19465 | 885 | 2.2 | 29.8% |
| 19466 | 47 | 1.1 | 8.5% |
| 19468 | 11,943 | 2.0 | 23.9% |
| 19472 | 42 | 1.8 | 26.2% |
| 19473 | 6,775 | 2.0 | 25.1% |
| 19474 | 925 | 1.6 | 15.8% |
| 19477 | 523 | 1.1 | 17.6% |
| 19478 | 89 | 1.5 | 4.5% |
| 19481 | 76 | 2.4 | 23.7% |
| 19482 | 22 | 2.3 | 31.8% |
| 19486 | 126 | 1.9 | 22.2% |
| 19490 | 582 | 2.7 | 31.6% |
| 19492 | 203 | 3.2 | 41.4% |
| 19504 | 379 | 3.3 | 42.7% |
| 19505 | 65 | 2.1 | 30.8% |
| 19512 | 308 | 2.2 | 26.0% |
| 19525 | 5,581 | 2.7 | 33.4% |
ZIP codes with the highest share of high results (100+ tests): 18070 (46.9%), 19504 (42.7%), 19009 (41.5%), 19492 (41.4%), 19408 (40.1%).
Results by community
Communities as written in the mailing address of the tested home, with at least 30 tests.
| Community | Tests | Median (pCi/L) | At or above 4 pCi/L |
|---|---|---|---|
| Lansdale | 25,941 | 1.9 | 20.7% |
| Norristown | 20,960 | 1.7 | 19.0% |
| Collegeville | 20,081 | 2.0 | 26.4% |
| Ambler | 15,698 | 2.1 | 24.2% |
| Pottstown | 14,922 | 2.3 | 27.9% |
| North Wales | 13,613 | 2.1 | 23.2% |
| Blue Bell | 12,242 | 2.1 | 23.5% |
| Glenside | 11,527 | 2.3 | 22.9% |
| Harleysville | 10,916 | 2.1 | 24.9% |
| Huntingdon Valley | 10,162 | 2.4 | 28.2% |
| Royersford | 9,450 | 2.1 | 25.6% |
| King Of Prussia | 9,321 | 1.8 | 19.2% |
| Wynnewood | 9,296 | 2.3 | 22.6% |
| Conshohocken | 8,683 | 2.2 | 23.9% |
| Hatboro | 7,211 | 2.1 | 21.2% |
| Elkins Park | 7,117 | 2.4 | 29.4% |
| Abington | 7,055 | 2.1 | 19.8% |
| Horsham | 6,953 | 1.8 | 19.8% |
| Willow Grove | 6,596 | 1.7 | 10.2% |
| Schwenksville | 6,576 | 2.0 | 25.1% |
| Lafayette Hill | 6,233 | 2.2 | 21.9% |
| Bala Cynwyd | 6,214 | 2.4 | 29.1% |
| Hatfield | 6,167 | 2.1 | 20.4% |
| Jenkintown | 5,974 | 2.9 | 35.0% |
| Plymouth Meeting | 5,699 | 1.9 | 20.2% |
| Gilbertsville | 5,579 | 2.8 | 33.4% |
| Bryn Mawr | 5,157 | 2.0 | 20.5% |
| Souderton | 4,536 | 2.2 | 24.7% |
| Oreland | 4,337 | 2.8 | 30.8% |
| Narberth | 4,023 | 2.4 | 27.5% |
| Merion Station | 3,866 | 2.5 | 30.5% |
| Fort Washington | 3,785 | 2.2 | 22.5% |
| Cheltenham | 3,747 | 2.3 | 20.5% |
| Telford | 3,691 | 2.2 | 25.2% |
| Dresher | 3,628 | 2.1 | 21.3% |
| Gladwyne | 3,614 | 2.5 | 30.9% |
| Ardmore | 3,583 | 1.7 | 14.8% |
| Audubon | 3,315 | 2.6 | 36.2% |
| Wyncote | 3,108 | 2.7 | 33.5% |
| Eagleville | 3,084 | 2.4 | 32.2% |
City pages in Montgomery County
Abington (19.8%) · Ambler (24.2%) · Ardmore (14.5%) · Bala Cynwyd (29.1%) · Blue Bell (23.5%) · Collegeville (26.5%) · Conshohocken (24.0%) · Elkins Park (29.4%) · Gilbertsville (33.5%) · Glenside (22.9%) · Harleysville (24.8%) · Hatboro (21.1%) · Hatfield (20.5%) · Horsham (19.7%) · Huntingdon Valley (28.1%) · Jenkintown (35.0%) · King of Prussia (19.2%) · Lafayette Hill (21.8%) · Lansdale (20.7%) · Norristown (19.0%) · North Wales (23.2%) · Plymouth Meeting (20.2%) · Pottstown (28.2%) · Royersford (25.6%) · Schwenksville (25.0%) · Willow Grove (10.2%) · Wynnewood (22.5%)
Results by floor of the home
Radon usually comes from the ground, so levels are typically highest in the lowest part of the home. In Montgomery County:
| Floor tested | Tests | Median (pCi/L) | At or above 4 pCi/L |
|---|---|---|---|
| Basement | 297,129 | 2.4 | 28.2% |
| First Floor | 54,743 | 1.3 | 12.0% |
| Slab On Grade | 17,128 | 1.8 | 16.2% |
| Second Floor | 7,852 | 1.1 | 8.6% |
| Crawl Space | 3,068 | 1.6 | 11.1% |
Recent tests (2016 to 2026)
Looking only at the 108,313 tests since 2016, 22.9% were at or above 4 pCi/L and the median was 2.1 pCi/L, compared with 24.6% and 2.1 pCi/L for all years.
Radon mitigation in Montgomery County
- Cost: the median reported cost of 2,476 mitigation systems installed in Montgomery County from 2022 to 2026 was $1,325.
- Results: for systems installed since 2016, the median test before mitigation was 6.2 pCi/L and the median test after mitigation was 1.1 pCi/L.
- Pennsylvania requires radon mitigation contractors to be certified by DEP. Find one in the DEP radon services directory or call 1-800-23-RADON.
Compare prices across states in our radon mitigation cost guide.
How to test your home in Montgomery County
- Short-term kits are sold at hardware stores and by Pennsylvania-certified labs; PA DEP says they typically cost about $20 to $30.
- Test the lowest lived-in level of the home with windows and doors closed.
- For a home sale, use a DEP-certified radon tester.
- 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 on Pennsylvania rules, contacts and every county’s EPA zone: Radon in Pennsylvania.
Frequently asked questions
Is radon a problem in Montgomery County?
24.6% of the 389,643 radon tests on record with PA DEP for Montgomery County were at or above 4 pCi/L, and the county is in EPA radon Zone 1. Any home can have high radon, so testing is the only way to know.
What is the average radon level in Montgomery County?
The median of all PA DEP test results in Montgomery County is 2.1 pCi/L. We use the median because a few very high readings would distort a simple average.
How much does radon mitigation cost in Montgomery County?
The median reported cost of 2,476 systems installed in Montgomery County from 2022 to 2026 was $1,325, according to PA DEP mitigation records.
Which ZIP codes in Montgomery County have the most radon?
Among ZIP codes with 100 or more tests, the highest shares of results at or above 4 pCi/L are in 18070 (46.9%), 19504 (42.7%), 19009 (41.5%).
Sources and method
Test statistics use the Pennsylvania DEP radon test database (about 3.4 million tests from 1986 to October 2026), limited to residential and unspecified buildings. Records can include repeat tests of the same home and some tests made after mitigation. Mitigation cost and before/after results come from the PA DEP radon mitigation system database. ZIP codes and communities with few tests are left out. Data retrieved November 2026.