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Radon Levels in Philadelphia County, Pennsylvania

EPA puts Philadelphia County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 10.6% of 8,442 (2020) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    10.6%

    19.7 pts below PA

    Philadelphia
    10.6%
    PA
    30.3%

    8,442 tests, 2020

  • Median result

    1.7pCi/L

    Below action level

    Philadelphia
    1.7 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2020

  • Tests reported

    8,442

    2nd of 63 by tests

    Philadelphia
    8,442
    Montgomery
    10,508

    Reported to CDC before any fix, 2020

  • EPA radon zone

    Zone 3

    Lower potential

    1. 1
    2. 2
    3. Zone 3

    1 highest, 3 lowest

    EPA predicts under 2 pCi/L indoors

  • Rank in PA

    63 of 63

    Lowest quarter

    Philadelphia
    10.6%
    Perry
    57.7%

    By share, of 63 with 30+ tests

Read a result for Philadelphia County

Starts at Philadelphia County's median, 1.7 pCi/L

1.7pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 1.7 pCi/L

Below 2 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Philadelphia County's median reported result, 2020.

Interpret this reading

The data

Philadelphia County, At a glance

Philadelphia County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Philadelphia County as a whole is an average indoor of less than 2 pCi/L (less than 75 Bq/m³). A low zone clears no address in it: homes above EPA's turn up in all three zones.

USGS geologic potential: Moderate across 64% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Philadelphia County, 2020

Share of reported tests at or above 4 pCi/L, by year, Philadelphia County
Share of reported tests at or above 4 pCi/L, by year, Philadelphia County
YearShare of reported tests at or above 4 pCi/L
201413.6%
201511.3%
201610.8%
201711.0%
20189.6%
20199.7%
202010.6%

2020: 10.6%. Across these years the share ran from 9.6% to 13.6%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 8,442 tests reported to CDC for Philadelphia County over 2020, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2020. Measured data period: 2005 to 2020 (every CDC figure on file).

How to read these figures

Philadelphia County, Compared

Philadelphia County radon figures, compared

Calculated by Radon411

Philadelphia County reports fewer high tests than Pennsylvania overall. 10.6% of its 8,442 tests in 2020 were at or above 4 pCi/L. That is 19.7 points below the 30.3% pooled from 67 Pennsylvania counties.

Ordered from highest share down, it comes 63rd of 63 Pennsylvania counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 25.5%; Philadelphia County sits 14.9 points below it.

Next door, the shares run from 7.0% in Burlington County, NJ to 23.2% in Bucks County, with Camden County, NJ and Burlington County, NJ below Philadelphia County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 10.6% share point the same way here.

Half the tests came in under 1.7 pCi/L and half over it; the single highest reached 78.8 pCi/L. The rest split 58.4% under 2 pCi/L and 31.0% from 2 to 4 (Pennsylvania: 44.3% and 25.4%). Year by year, 2014 opened at 13.6% and 2020 closed at 10.6% (down 3.0 points), with 2014 the high at 13.6%.

The busiest year on file was 2020, with 8,442 tests reported; the quietest, 2014, had 4,510.

Share of reported tests at or above 4 pCi/L by year, Philadelphia County against Pennsylvania2014 to 2020, years with 30 or more tests: Philadelphia County 13.6% to 10.6%, the state's pooled share 30.3% in 2020.
Philadelphia CountyPennsylvania, pooled
Share of reported tests at or above 4 pCi/L by year, Philadelphia County against Pennsylvania: data table
YearTestsPhiladelphia County, at or above 4 pCi/LPennsylvania, pooled
20144,51013.6%36.1%
20155,68111.3%37.8%
20166,71910.8%34.4%
20176,72111.0%35.1%
20187,3469.6%30.5%
20197,5959.7%31.4%
20208,44210.6%30.3%
Philadelphia County against Pennsylvania, the United States and nearby counties, 2020
AreaTestsAt or above 4 pCi/LMedianDifference from Philadelphia County
Philadelphia County8,44210.6%1.7 pCi/LThis county
Pennsylvania, pooled67 counties, pooled93,66930.3%Not pooled+19.7 points
United States, pooled915 counties, pooled405,35525.5%Not pooled+14.9 points
Perry Countyhighest in the state18957.7%4.9 pCi/L+47.1 points
Fayette Countylowest in the state28717.4%1.8 pCi/L+6.8 points
Bucks County, PAborders it7,06623.2%2.0 pCi/L+12.6 points
Montgomery County, PAborders it10,50821.8%2.0 pCi/L+11.2 points
Delaware County, PAborders it6,04114.7%1.8 pCi/L+4.1 points
Gloucester County, NJborders it4,45313.5%1.2 pCi/L+2.9 points
Camden County, NJborders it7,6579.4%1.0 pCi/L−1.2 points
Burlington County, NJborders it6,7857.0%0.9 pCi/L−3.6 points
Where Philadelphia County's reported results fell, 2020, beside Pennsylvania and the United States
ResultPhiladelphia County testsPhiladelphia County sharePennsylvania shareU.S. shareAgainst Pennsylvania
Under 2 pCi/L4,92758.4%44.3%51.6%+14.1 points
2 to 4 pCi/L2,61831.0%25.4%22.9%+5.6 points
4 pCi/L and above89710.6%30.3%25.5%−19.7 points
Philadelphia County ranked among the 63 Pennsylvania counties with 30 or more tests, by share at or above 4 pCi/L, 2020
CountyRankTestsAt or above 4 pCi/LMedian
Luzerne County53 of 6399128.2%2.0 pCi/L
Lackawanna County54 of 6377627.1%2.1 pCi/L
Chester County55 of 636,77024.0%2.0 pCi/L
Bucks County56 of 637,06623.2%2.0 pCi/L
Erie County57 of 631,16222.2%1.9 pCi/L
Montgomery County58 of 6310,50821.8%2.0 pCi/L
Greene County59 of 634520.0%3.2 pCi/L
Potter County60 of 6319517.9%1.1 pCi/L
Fayette County61 of 6328717.4%1.8 pCi/L
Delaware County62 of 636,04114.7%1.8 pCi/L
Philadelphia County63 of 638,44210.6%1.7 pCi/L
Philadelphia County radon tests by year, against Pennsylvania's pooled share
YearTestsAt or above 4 pCi/LMedianHighestPennsylvania, pooledChange from the row before
20208,44210.6%1.7 pCi/L78.8 pCi/L30.3%+0.9 points
20197,5959.7%1.6 pCi/L112.4 pCi/L31.4%+0.1 points
20187,3469.6%1.5 pCi/L63.4 pCi/L30.5%−1.4 points
20176,72111.0%1.6 pCi/L84.2 pCi/L35.1%+0.2 points
20166,71910.8%1.6 pCi/L71.6 pCi/L34.4%−0.5 points
20155,68111.3%1.6 pCi/L99.8 pCi/L37.8%−2.3 points
20144,51013.6%1.7 pCi/L68.6 pCi/L36.1%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Philadelphia County, State data

Pennsylvania's own radon test data

Measured

What Pennsylvania's own agencies publish about radon tests in Philadelphia County, with their period. These are not CDC's figures and are never added to them.

MeasuredState figures, not CDC's

What Pennsylvania DEP reports for the ZIP codes in Philadelphia County

Pennsylvania DEP publishes its figures by ZIP code, not by county. These are the 49 ZIP codes that lie wholly or partly in Philadelphia County, each with the state's own figures for it. Period: Period not stated by DEP.

ZIP codes in Philadelphia County
ZIP codeWhat the state reports
19102Basement: average 1.8 pCi/L, 126 tests; First floor: figures not shown
19103Basement: average 1.9 pCi/L, 1,153 tests; First floor: average 1.0 pCi/L, 275 tests
19104Basement: average 2.2 pCi/L, 905 tests; First floor: average 1.2 pCi/L, 175 tests
19106Basement: average 2.0 pCi/L, 845 tests; First floor: average 1.2 pCi/L, 191 tests
19107Basement: average 1.5 pCi/L, 563 tests; First floor: average 0.9 pCi/L, 89 tests
19108Basement: figures not shown; First floor: figures not shown
19109Basement: figures not shown; First floor: figures not shown
19111Basement: average 2.7 pCi/L, 3,433 tests; First floor: average 1.7 pCi/L, 765 tests
19112Basement: figures not shown; First floor: figures not shown
19114Basement: average 2.4 pCi/L, 1,369 tests; First floor: average 1.3 pCi/L, 406 tests
19115Basement: average 3.3 pCi/L, 1,944 tests; First floor: average 2.2 pCi/L, 536 tests
19116Basement: average 3.4 pCi/L, 1,816 tests; First floor: average 1.9 pCi/L, 527 tests
19118Basement: average 4.5 pCi/L, 2,852 tests; First floor: average 2.4 pCi/L, 854 tests
19119Basement: average 3.1 pCi/L, 4,008 tests; First floor: average 1.7 pCi/L, 851 tests
19120Basement: average 1.5 pCi/L, 1,222 tests; First floor: average 1.0 pCi/L, 253 tests
19121Basement: average 1.7 pCi/L, 1,005 tests; First floor: average 1.0 pCi/L, 53 tests
19122Basement: average 1.6 pCi/L, 607 tests; First floor: average 1.1 pCi/L, 49 tests
19123Basement: average 2.2 pCi/L, 886 tests; First floor: average 1.4 pCi/L, 102 tests
19124Basement: average 4.6 pCi/L, 1,184 tests; First floor: average 1.8 pCi/L, 237 tests
19125Basement: average 2.1 pCi/L, 2,386 tests; First floor: average 1.3 pCi/L, 121 tests
19126Basement: average 2.3 pCi/L, 752 tests; First floor: average 1.4 pCi/L, 169 tests
19127Basement: average 2.8 pCi/L, 1,273 tests; First floor: average 1.9 pCi/L, 231 tests
19128Basement: average 3.2 pCi/L, 6,261 tests; First floor: average 2.1 pCi/L, 1,180 tests
19129Basement: average 3.0 pCi/L, 1,493 tests; First floor: average 1.5 pCi/L, 280 tests
19130Basement: average 2.0 pCi/L, 2,557 tests; First floor: average 1.2 pCi/L, 422 tests
19131Basement: average 2.1 pCi/L, 956 tests; First floor: average 1.3 pCi/L, 254 tests
19132Basement: average 1.9 pCi/L, 253 tests; First floor: figures not shown
19133Basement: average 2.4 pCi/L, 133 tests; First floor: figures not shown
19134Basement: average 1.8 pCi/L, 1,031 tests; First floor: average 1.0 pCi/L, 108 tests
19135Basement: average 1.6 pCi/L, 891 tests; First floor: average 1.4 pCi/L, 159 tests
19136Basement: average 1.7 pCi/L, 1,060 tests; First floor: average 1.5 pCi/L, 198 tests
19137Basement: average 2.0 pCi/L, 292 tests; First floor: figures not shown
19138Basement: average 1.4 pCi/L, 681 tests; First floor: average 1.2 pCi/L, 67 tests
19139Basement: average 1.7 pCi/L, 718 tests; First floor: average 1.1 pCi/L, 74 tests
19140Basement: average 1.9 pCi/L, 268 tests; First floor: average 1.0 pCi/L, 41 tests
19141Basement: average 1.5 pCi/L, 495 tests; First floor: average 1.0 pCi/L, 66 tests
19142Basement: average 1.3 pCi/L, 412 tests; First floor: average 0.8 pCi/L, 119 tests
19143Basement: average 1.7 pCi/L, 1,581 tests; First floor: average 1.2 pCi/L, 220 tests
19144Basement: average 3.2 pCi/L, 1,672 tests; First floor: average 1.6 pCi/L, 381 tests
19145Basement: average 1.5 pCi/L, 1,820 tests; First floor: average 1.2 pCi/L, 236 tests
19146Basement: average 1.8 pCi/L, 4,205 tests; First floor: average 1.2 pCi/L, 371 tests
19147Basement: average 1.9 pCi/L, 4,144 tests; First floor: average 1.2 pCi/L, 606 tests
19148Basement: average 1.9 pCi/L, 2,399 tests; First floor: average 1.1 pCi/L, 176 tests
19149Basement: average 1.6 pCi/L, 1,133 tests; First floor: average 1.4 pCi/L, 220 tests
19150Basement: average 1.9 pCi/L, 1,138 tests; First floor: average 1.4 pCi/L, 161 tests
19151Basement: average 2.6 pCi/L, 1,814 tests; First floor: average 1.3 pCi/L, 461 tests
19152Basement: average 1.9 pCi/L, 1,323 tests; First floor: average 1.4 pCi/L, 330 tests
19153Basement: average 0.9 pCi/L, 259 tests; First floor: average 0.6 pCi/L, 62 tests
19154Basement: average 1.5 pCi/L, 1,390 tests; First floor: average 1.1 pCi/L, 302 tests
  • DEP's report gives the number of tests, the highest result and the average result for each floor tested; it states no period.
  • DEP says the smartest thing to do is to test your home for radon, no matter where you live.
  • A ZIP code that crosses the county line is listed whole; its figures cover all of it.

Measured: Pennsylvania DEP data, Period not stated by DEP.

Philadelphia County, Geology

The ground under Philadelphia County

Predicted

USGS's geologic map splits Philadelphia County: 63.6% of its land is moderate radon potential and 36.5% high. The map puts 62.3% of Philadelphia County in the area it calls Atlantic Coastal Plain and 36.5% in Piedmont Lowland, with one smaller area beside them. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 14, in the high band (12 to 17).

USGS's geologic areas under Philadelphia County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Atlantic Coastal PlainGlacial deposits and marine sediments.Moderate1062.3%
Piedmont LowlandMica schist, phyllite, hornblende gneiss, and marble.High1436.5%
Inner Coastal PlainCretaceous-Lower Tertiary gravel, sand, silt, clay.Moderate101.2%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Philadelphia County beside the ground around it

Pennsylvania as a whole has more high-potential ground than Philadelphia County: 70.4% of its land, against 36.5% here. Of the 6 counties that border it, 3 have more high-potential ground, Montgomery County the most at 100%.

Share of land by USGS radon potential: Philadelphia County, the 6 counties bordering it and Pennsylvania
AreaEPA zoneLow potentialModerate potentialHigh potential
Philadelphia CountyZone 3None63.6%36.5%
Camden County, NJZone 274.2%25.8%None
Delaware CountyZone 1None23.4%76.6%
Montgomery CountyZone 1NoneNone100%
Gloucester County, NJZone 267.7%32.3%None
Bucks CountyZone 1None11.0%89.0%
Burlington County, NJZone 276.3%23.7%None
Pennsylvania67 counties, pooled by land areaVaries0.7%28.9%70.4%

The map rates the ground, not the air in any home.

Local help

Philadelphia County, Local resources

Radon testing and mitigation in Philadelphia County

Listed radon businesses with an address in Philadelphia County:

Listed radon professionals by town: Philadelphia

What Pennsylvania's program says
Phone
800-237-2366
Licensing of radon professionals
The Radon Certification Act requires DEP to establish by regulation, a certification program for persons conducting radon gas and radon progeny testing, laboratory analysis and mitigation of radon contamination in buildings.

What it means

Philadelphia County, Questions

Questions about radon in Philadelphia County

Are radon levels high in Philadelphia County?

In 2020, 10.6% of the radon tests reported to CDC for Philadelphia County, Pennsylvania were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.7 pCi/L. Of 63 Pennsylvania counties with 30 or more tests for the same period, 62 reported a higher share; pooled, the state comes to 30.3%.

Which counties border Philadelphia County?

Philadelphia County borders 6 counties: Camden County, NJ, Delaware County, PA, Montgomery County, PA, Gloucester County, NJ, Bucks County, PA and Burlington County, NJ.

Products

Philadelphia County, Products

Testing a home in Philadelphia County

In Philadelphia County, 10.6% of 8,442 tests reported to CDC in 2020 reached 4 pCi/L, against 30.3% pooled across Pennsylvania. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Philadelphia County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Philadelphia County homes, compared

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Philadelphia County, Bordering counties

Counties bordering Philadelphia County

Calculated by Radon411

Philadelphia County, Cities and towns

Cities and towns in Philadelphia County

About 1,574,281 people live in Philadelphia County by the Census Bureau's estimate for July 1, 2025, 26,456 fewer than in 2020 (−1.7%). Packed into its land, that is 11,717 people per square mile. Philadelphia, its one incorporated place, has 1,574,281 residents, 100.0% of the total. CDC's 8,442 reported tests for 2020 work out to 5.4 per 1,000 residents (2025 estimate), close to Pennsylvania's 7.2.

Philadelphia is the one incorporated place here; CDC publishes no figure by town, so it reads Philadelphia County's.

Philadelphia, Philadelphia County: residents on July 1, 2025
PlaceResidentsSince 2020Share of residents
Philadelphia1,574,281−1.7%100.0%

One incorporated place, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Philadelphia County, Homes

Homes in Philadelphia County

Fewer than six in ten of Philadelphia County's 739,725 homes are detached houses (8%, against 57% across Pennsylvania); the rest are attached, in shared buildings or mobile. The homes are older than Pennsylvania's as a whole: half were built before 1949 (1965 for Pennsylvania), and 66% date from before 1960. 52% of occupied homes are lived in by their owner (Pennsylvania: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Philadelphia County, Pennsylvania, 2019 to 2023
HomesPhiladelphia CountyPennsylvania
Housing units739,7255,779,663
Detached houses8%57%
In buildings of 5 or more21%13%
Mobile homesunder 1%4%
Built before 196066%45%
Built since 20009%14%
Middle year built19491965
Owner-occupied52%69%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.