Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Monmouth County, New Jersey
EPA puts Monmouth County in Zone 1, its highest radon zone, and most reported tests there come back low, though 9.8% of 9,745 (2022) reached 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
9.8%
0.1 pts above NJ
- Monmouth
- 9.8%
- New Jersey
- 9.7%
9,745 tests, 2022
Median result
0.7pCi/L
Below action level
- Monmouth
- 0.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2022
Tests reported
9,745
3rd of 21 by tests
- Monmouth
- 9,745
- 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
9 of 21
Middle half
- Monmouth
- 9.8%
- Warren
- 24.6%
By share, of 21 with 30+ tests
Read a result for Monmouth County
Starts at Monmouth County's median, 0.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.7 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. Monmouth County's median reported result, 2022.
The data
Monmouth County, At a glance
Monmouth County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Monmouth County in
USGS geologic potential: Low across 60% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Monmouth County, 2022
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 12.4% |
| 2015 | 11.4% |
| 2016 | 11.1% |
| 2017 | 11.6% |
| 2018 | 11.1% |
| 2019 | 10.0% |
| 2020 | 11.2% |
| 2021 | 10.2% |
| 2022 | 9.8% |
2022: 9.8%. Across these years the share ran from 9.8% to 12.4%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 9,745 tests reported to CDC for Monmouth 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).
Monmouth County, Compared
Monmouth County radon figures, compared
Calculated by Radon4119.8% of its 9,745 tests in 2022 were at or above 4 pCi/L. That is 0.1 points above the 9.7% pooled from 21 New Jersey counties.
Ordered from highest share down, it comes 9th of 21 New Jersey counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 23.9%; Monmouth County sits 14.1 points below it.
Next door, the shares run from 1.8% in Ocean County to 10.6% in Mercer County, with Middlesex County, Burlington County and Ocean County below Monmouth County. The reported tests do not follow EPA's Zone 1 label for Monmouth County (predicted average above 4 pCi/L): 9.8% of them reached 4 pCi/L, fewer than that label suggests.
Half the tests came in under 0.7 pCi/L and half over it; the single highest reached 77.6 pCi/L. The rest split 77.0% under 2 pCi/L and 13.2% from 2 to 4 (New Jersey: 74.9% and 15.4%). Year by year, 2014 opened at 12.4% and 2022 closed at 9.8% (down 2.6 points), with 2014 the high at 12.4%.
The busiest year on file was 2020, with 11,803 tests reported; the quietest, 2014, had 7,421.
Monmouth CountyNew Jersey, pooled
| Year | Tests | Monmouth County, at or above 4 pCi/L | New Jersey, pooled |
|---|---|---|---|
| 2014 | 7,421 | 12.4% | 12.8% |
| 2015 | 8,220 | 11.4% | 12.5% |
| 2016 | 9,661 | 11.1% | 12.5% |
| 2017 | 9,810 | 11.6% | 11.9% |
| 2018 | 9,637 | 11.1% | 11.0% |
| 2019 | 9,952 | 10.0% | 11.2% |
| 2020 | 11,803 | 11.2% | 11.7% |
| 2021 | 10,548 | 10.2% | 10.3% |
| 2022 | 9,745 | 9.8% | 9.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Monmouth County, Geology
The ground under Monmouth County
PredictedUSGS's geologic map splits Monmouth County: 60.3% of its land is low radon potential and 36.5% moderate. The map puts 60.3% of Monmouth County in the area it calls Outer Coastal Plain and 36.5% in Inner Coastal Plain. USGS gives the first a radon index of 8, in the low band (5 to 8), and the second 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Outer Coastal Plain | Upper Tertiary-Quaternary gravel, sand, silt, clay. | Low | 8 | 60.3% |
| Inner Coastal Plain | Cretaceous-Lower Tertiary gravel, sand, silt, clay. | Moderate | 10 | 36.5% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Monmouth County beside the ground around it
Across New Jersey 29.8% of the land is rated high; none of Monmouth County's is. Of the 4 counties that border it, 2 have more high-potential ground, Mercer County the most at 50.5%.
The map rates the ground, not the air in any home.
Local help
Monmouth County, Local resources
Radon testing and mitigation in Monmouth County
Listed radon businesses with an address in Monmouth 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.
Listed radon professionals by town: Asbury Park, Freehold
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
Monmouth County, Questions
Questions about radon in Monmouth County
Are radon levels high in Monmouth County?
In 2022, 9.8% of the radon tests reported to CDC for Monmouth County, New Jersey were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.7 pCi/L. Of 21 New Jersey counties with 30 or more tests for the same period, 8 reported a higher share; pooled, the state comes to 9.7%.
Which counties border Monmouth County?
Monmouth County borders 4 counties: Middlesex County, Mercer County, Ocean County and Burlington County.
Products
Monmouth County, Products
Testing a home in Monmouth County
In Monmouth County, 9.8% of 9,745 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 Monmouth 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
MonitorINKBIRD
INK-RD3 battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
First reading: Within 24 hours
Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Monmouth County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Monmouth County
Explore
Monmouth County, Bordering counties
Counties bordering Monmouth County
Calculated by Radon411- Radon levels in Mercer CountyEPA zone 1
10.6%at or above 4 pCi/L
Median 0.9 pCi/L · 6,370 tests · 0.8 points above Monmouth County
- Radon levels in Middlesex CountyEPA zone 2
7.3%at or above 4 pCi/L
Median 0.8 pCi/L · 9,594 tests · 2.5 points below Monmouth County
- Radon levels in Burlington CountyEPA zone 2
6.2%at or above 4 pCi/L
Median 0.9 pCi/L · 5,355 tests · 3.6 points below Monmouth County
- Radon levels in Ocean CountyEPA zone 3
1.8%at or above 4 pCi/L
Median 0.5 pCi/L · 2,604 tests · 8.0 points below Monmouth County
Monmouth County, Cities and towns
Cities and towns in Monmouth County
The Census Bureau estimates 651,035 residents in Monmouth County for July 1, 2025, 8,650 more than in 2020 (+1.3%). Packed into its land, that is 1,391 people per square mile. No town dominates: Long Branch, the largest, has 33,321 residents, 5.1% of the total. Together its 38 incorporated places hold 36.8% of those residents; the other 63.2% live outside any of them. CDC's 9,745 reported tests for 2022 work out to 15.0 per 1,000 residents (2025 estimate), close to New Jersey's 11.4.
From Long Branch to Loch Arbour, CDC publishes no figure by town: each reads Monmouth County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Long Branch | 33,321 | +5.2% | 5.1% |
| Tinton Falls | 19,539 | +2.3% | 3.0% |
| Asbury Park | 15,632 | +3.1% | 2.4% |
| Eatontown | 13,607 | +0.5% | 2.1% |
| Red Bank | 12,896 | −0.1% | 2.0% |
| Freehold | 12,562 | +0.4% | 1.9% |
| Keansburg | 9,818 | +0.8% | 1.5% |
| Matawan | 9,768 | +2.4% | 1.5% |
| West Long Branch | 8,625 | +0.5% | 1.3% |
| Keyport | 7,235 | +0.6% | 1.1% |
| Rumson | 7,157 | −2.2% | 1.1% |
| Oceanport | 6,540 | +6.4% | 1.0% |
Places in Monmouth County with a city page: 1 of 1
- Little Silver
- Fair Haven
- Manasquan
- Belmar
- Union Beach
- Brielle
- Spring Lake Heights
- Neptune City
- Atlantic Highlands
- Highlands
- Shrewsbury
- Bradley Beach
- Monmouth Beach
- Spring Lake
- Englishtown
- Avon-by-the-Sea
- Sea Girt
- Allentown
- Lake Como
- Farmingdale
- Sea Bright
- Deal
- Interlaken
- Roosevelt
The other 2 places in Monmouth County
- Allenhurst
- Loch Arbour
38 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).
Monmouth County, Homes
Homes in Monmouth County
Of Monmouth County's 269,728 homes, 66% are detached houses, against 53% across New Jersey; 17% are in buildings of five or more homes. Half of its homes were built before 1975, close to New Jersey's 1969: 30% date from before 1960 and 16% from 2000 or later. Owners live in 75% of the occupied homes (New Jersey: 64%), so for most households a test and a fix are their own to order.
| Homes | Monmouth County | New Jersey |
|---|---|---|
| Housing units | 269,728 | 3,775,842 |
| Detached houses | 66% | 53% |
| In buildings of 5 or more | 17% | 22% |
| Mobile homes | 1% | 1% |
| Built before 1960 | 30% | 38% |
| Built since 2000 | 16% | 15% |
| Middle year built | 1975 | 1969 |
| Owner-occupied | 75% | 64% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.