Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Somerset County, New Jersey
EPA puts Somerset County in Zone 1, its highest radon zone, and 15.4% of its 7,679 reported radon tests (2022) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
15.4%
5.7 pts above NJ
- Somerset
- 15.4%
- New Jersey
- 9.7%
7,679 tests, 2022
Median result
1.2pCi/L
Below action level
- Somerset
- 1.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2022
Tests reported
7,679
6th of 21 by tests
- Somerset
- 7,679
- Bergen
- 11,440
Reported to CDC before any fix, 2022
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in New Jersey
4 of 21
Top quarter
- Somerset
- 15.4%
- Warren
- 24.6%
By share, of 21 with 30+ tests
Read a result for Somerset County
Starts at Somerset County's median, 1.2 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.2 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Somerset County's median reported result, 2022.
The data
Somerset County, At a glance
Somerset County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Somerset County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Somerset County, 2022
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 19.0% |
| 2015 | 18.6% |
| 2016 | 20.1% |
| 2017 | 18.7% |
| 2018 | 16.8% |
| 2019 | 17.4% |
| 2020 | 17.6% |
| 2021 | 16.4% |
| 2022 | 15.4% |
2022: 15.4%. Across these years the share ran from 15.4% to 20.1%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 7,679 tests reported to CDC for Somerset County over 2022, 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: 2022. Measured data period: 2014 to 2022 (every CDC figure on file).
Somerset County, Compared
Somerset County radon figures, compared
Calculated by Radon411Somerset County's 7,679 reported tests in 2022 had a middle value of 1.2 pCi/L and a maximum of 125.6 pCi/L, and 15.4% reached 4 pCi/L. New Jersey as a whole (21 New Jersey counties, pooled) comes to 9.7%: 5.7 points lower than here.
Among its state's counties it ranks 4th of 21 New Jersey counties with 30 or more tests for the same period. Statewide for the same period, Warren County reported the highest share (24.6%) and Cape May County the lowest (0.0%).
Below the action level, 5,007 tests (65.2%) came in under 2 pCi/L, against 74.9% statewide, and 1,491 tests (19.4%) fell between 2 and 4, against 15.4% statewide. The busiest year on file was 2021, with 8,719 tests reported; the quietest, 2014, had 6,363.
EPA's 1993 zone map puts Somerset County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.
Next door, the shares run from 5.1% in Union County to 21.1% in Hunterdon County, with Morris County, Mercer County and Middlesex County below Somerset County. Over 9 years of annual figures the share fell 3.6 points, from 19.0% in 2014 to 15.4% in 2022; its peak was 20.1% in 2016.
Somerset CountyNew Jersey, pooled
| Year | Tests | Somerset County, at or above 4 pCi/L | New Jersey, pooled |
|---|---|---|---|
| 2014 | 6,363 | 19.0% | 12.8% |
| 2015 | 6,738 | 18.6% | 12.5% |
| 2016 | 6,989 | 20.1% | 12.5% |
| 2017 | 7,287 | 18.7% | 11.9% |
| 2018 | 7,357 | 16.8% | 11.0% |
| 2019 | 8,196 | 17.4% | 11.2% |
| 2020 | 8,685 | 17.6% | 11.7% |
| 2021 | 8,719 | 16.4% | 10.3% |
| 2022 | 7,679 | 15.4% | 9.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Somerset County, Geology
The ground under Somerset County
PredictedUSGS's geologic map puts all of Somerset County's mapped land in one class: high radon potential. All of it lies in the area the map calls Southern Piedmont, to which USGS gives a radon index of 14, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Southern Piedmont | Black shale, sandstone and siltstone. | High | 14 | 99.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Somerset County beside the ground around it
Somerset County has more high-potential ground than New Jersey as a whole: 100% of its land against 29.8%. Of the 5 counties that border it, none has as large a share of high-potential ground; Hunterdon County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Somerset County, Local resources
Radon testing and mitigation in Somerset County
- Radon SectionRadon Section, run by New Jersey Department of Environmental Protection, licenses or certifies radon professionals, offers free or discounted test kits and states the rule for disclosing radon when a home is sold, and answers questions about testing and mitigation in New Jersey.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Check with your municipal or county health department for free radon test kits or purchase a test kit from a hardware store or a NJ certified radon business.
- Compare kits
- Professionals in New Jersey15 professionals are listed in New Jersey.
What New Jersey's program says
- Phone
- 800-648-0394
- Licensing of radon professionals
By law, all businesses and professionals conducting radon testing and mitigation in New Jersey must be certified by the DEP.
- Disclosure when a home is sold or rented
Under the law, the seller must provide the buyer, at the time the contract of sale is entered into, with a copy of the results of the radon test and evidence of any mitigation or treatment.
What it means
Somerset County, Questions
Questions about radon in Somerset County
Are radon levels high in Somerset County?
In 2022, 15.4% of the radon tests reported to CDC for Somerset County, New Jersey were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.2 pCi/L. Of 21 New Jersey counties with 30 or more tests for the same period, 3 reported a higher share; pooled, the state comes to 9.7%.
Which counties border Somerset County?
Somerset County borders 5 counties: Middlesex County, Hunterdon County, Union County, Mercer County and Morris County.
Products
Somerset County, Products
Testing a home in Somerset County
In Somerset County, 15.4% of 7,679 tests reported to CDC in 2022 reached 4 pCi/L, against 9.7% pooled across New Jersey. In Zone 1 the year-round level in Somerset County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
MonitorAEGTEST
HOUND-1011 rechargeable radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Somerset County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Somerset County
Explore
Somerset County, Bordering counties
Counties bordering Somerset County
Calculated by Radon411- Radon levels in Hunterdon CountyEPA zone 1
21.1%at or above 4 pCi/L
Median 1.4 pCi/L · 3,748 tests · 5.7 points above Somerset County
- Radon levels in Morris CountyEPA zone 1
13.6%at or above 4 pCi/L
Median 1.1 pCi/L · 10,939 tests · 1.8 points below Somerset County
- Radon levels in Mercer CountyEPA zone 1
10.6%at or above 4 pCi/L
Median 0.9 pCi/L · 6,370 tests · 4.8 points below Somerset County
- Radon levels in Middlesex CountyEPA zone 2
7.3%at or above 4 pCi/L
Median 0.8 pCi/L · 9,594 tests · 8.1 points below Somerset County
- Radon levels in Union CountyEPA zone 2
5.1%at or above 4 pCi/L
Median 0.9 pCi/L · 6,111 tests · 10.3 points below Somerset County
Somerset County, Cities and towns
Cities and towns in Somerset County
The Census Bureau estimates 356,486 residents in Somerset County for July 1, 2025, 11,970 more than in 2020 (+3.5%). Packed into its land, that is 1,181 people per square mile. No town dominates: North Plainfield, the largest, has 22,879 residents, 6.4% of the total. Together its 12 incorporated places hold 26.4% of those residents; the other 73.6% live outside any of them. Testing is reported here more often than across the state: CDC's 7,679 reported tests for 2022 come to 21.5 for every 1,000 residents (2025 estimate), against 11.4 for New Jersey.
From North Plainfield to Millstone, CDC publishes no figure by town: each reads Somerset County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| North Plainfield | 22,879 | +0.6% | 6.4% |
| Somerville | 14,665 | +18.7% | 4.1% |
| Bound Brook | 13,038 | +9.1% | 3.7% |
| Manville | 10,932 | +0.1% | 3.1% |
| Raritan | 8,516 | +8.9% | 2.4% |
| Bernardsville | 7,966 | +1.2% | 2.2% |
| Watchung | 6,583 | +2.3% | 1.8% |
| South Bound Brook | 4,926 | +1.5% | 1.4% |
| Peapack and Gladstone | 2,587 | +1.2% | 0.7% |
| Far Hills | 974 | +5.1% | 0.3% |
| Rocky Hill | 751 | +1.6% | 0.2% |
| Millstone | 456 | +0.4% | 0.1% |
12 incorporated places, 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).
Somerset County, Homes
Homes in Somerset County
Of Somerset County's 132,831 homes, 59% are detached houses, against 53% across New Jersey; 17% are in buildings of five or more homes. Much of Somerset County is recent building: 16% of its homes have gone up since 2000 and the middle year built is 1982, against 1969 for New Jersey. 74% of occupied homes are lived in by their owner (New Jersey: 64%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Somerset County | New Jersey |
|---|---|---|
| Housing units | 132,831 | 3,775,842 |
| Detached houses | 59% | 53% |
| In buildings of 5 or more | 17% | 22% |
| Mobile homes | under 1% | 1% |
| Built before 1960 | 25% | 38% |
| Built since 2000 | 16% | 15% |
| Middle year built | 1982 | 1969 |
| Owner-occupied | 74% | 64% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.