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 Foster County, North Dakota
EPA puts Foster County in Zone 1, its highest radon zone, and high results are common there: 61.3% of the 31 radon tests reported to CDC (2008 to 2017, laboratory totals) came back 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
61.3%
2.0 pts above ND
- Foster
- 61.3%
- ND
- 59.3%
31 tests, 2008 to 2017
Median result
4.5pCi/L
Action level reached
- Foster
- 4.5 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
31
29th of 29 by tests
- Foster
- 31
- Burleigh
- 1,558
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in ND
19 of 29
Middle half
- Foster
- 61.3%
- Pembina
- 82.5%
By share, of 29 with 30+ tests
Read a result for Foster County
Starts at Foster County's median, 4.5 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.5 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Foster County's median reported result, 2008 to 2017.
The data
Foster County, At a glance
Foster County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Foster 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 Foster County, 2008 to 2017, laboratory
Under 2 pCi/L: 13%2 to 4 pCi/L: 26%4 pCi/L and above: 61%
Of 31 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 4 | 12.9% |
| 2 to 4 pCi/L | 8 | 25.8% |
| 4 pCi/L and above | 19 | 61.3% |
What these figures count
These are the 31 tests reported to CDC for Foster County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Foster County, Compared
Foster County radon figures, compared
Calculated by Radon411More than half: 61.3% of the 31 radon tests reported to CDC for Foster County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 19th of 29 North Dakota counties with 30 or more tests for the same period. That is 2.0 points above the 59.3% pooled from 53 North Dakota counties.
The median result, 4.5 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 20.3 pCi/L. The rest split 12.9% under 2 pCi/L and 25.8% from 2 to 4 (North Dakota: 18.3% and 22.4%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 61.3% share point the same way here.
1 of its 2 bordering counties with figures ran higher, led by Stutsman County at 73.5%; Wells County reported 48.1%. Statewide for the same period, Pembina County reported the highest share (82.5%) and Williams County the lowest (33.8%).
CDC's ten-year totals for Foster County went from 22 tests (2005 to 2014) to 31 (2008 to 2017), the share going from 50.0% to 61.3%.
Nationally, every county with a figure for the same period pools to 35.7%; Foster County sits 25.6 points above it.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Foster County, Geology
The ground under Foster County
PredictedUSGS's geologic map puts all of Foster County's mapped land in one class: high radon potential. All of it lies in the area the map calls Great Plains (Glaciated), to which USGS gives a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Great Plains (Glaciated) | Glacial deposits derived from Cretaceous shales containing higher than average amounts of uranium. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Foster County beside the ground around it
On high-potential ground Foster County is close to North Dakota as a whole: 100% of its land against 98.9%. Of the 4 counties that border it, none has as large a share of high-potential ground; Eddy County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Foster County, Local resources
Radon testing and mitigation in Foster County
- North Dakota's radon programNorth Dakota Department of Environmental QualityNorth Dakota's radon program offers free or discounted test kits, and answers questions about testing and mitigation in North Dakota.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Notice: The DEQ is out of free radon test kits.
- Compare kits
- Professionals in North Dakota47 professionals are listed in North Dakota.
What North Dakota's program says
- Phone
- 701-328-5166
- jOtto@nd.gov
What it means
Foster County, Questions
Questions about radon in Foster County
Are radon levels high in Foster County?
Over the 2008 to 2017 laboratory totals, 61.3% of the radon tests reported to CDC for Foster County, North Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.5 pCi/L. Of 29 North Dakota counties with 30 or more tests for the same period, 18 reported a higher share; pooled, the state comes to 59.3%.
Which counties border Foster County?
Foster County borders 4 counties: Eddy County, Griggs County, Wells County and Stutsman County.
Products
Foster County, Products
Testing a home in Foster County
In Foster County, 61.3% of 31 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 59.3% pooled across North Dakota. In Zone 1 the year-round level in Foster 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
MonitorX-Sense
XR0A-SR battery digital radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
Short-term kit
RA100 short-term liquid scintillation radon test kit
- Lab fee extra
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
Foster County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Foster County
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Foster County, Bordering counties
Counties bordering Foster County
Calculated by Radon411- Radon levels in Stutsman CountyEPA zone 1
73.5%at or above 4 pCi/L
Median 5.8 pCi/L · 351 tests · 12.2 points above Foster County
- Radon levels in Griggs CountyEPA zone 1
54.5%at or above 4 pCi/L
Median 5.0 pCi/L · 11 tests · 6.8 points below Foster County
- Radon levels in Wells CountyEPA zone 1
48.1%at or above 4 pCi/L
Median 3.8 pCi/L · 81 tests · 13.2 points below Foster County
- Radon levels in Eddy CountyEPA zone 1
12.5%at or above 4 pCi/L
Median 0.9 pCi/L · 8 tests · 48.8 points below Foster County
Foster County, Cities and towns
Cities and towns in Foster County
Foster County has been losing residents: from 3,384 in 2020 to 3,212 on July 1, 2025, a fall of 5.1% by the Census Bureau's estimates. Spread over its land, that is 5.1 people to the square mile. Carrington alone is home to 1,950 of them, 60.7% of the total. Together its 4 incorporated places hold 67.1% of those residents; the other 32.9% live outside any of them. CDC's 31 reported tests for 2008 to 2017 work out to 9.7 per 1,000 residents (2025 estimate), close to North Dakota's 8.3.
From Carrington to Grace City, CDC publishes no figure by town: each reads Foster County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Carrington | 1,950 | −6.0% | 60.7% |
| Glenfield | 93 | −2.1% | 2.9% |
| McHenry | 60 | −4.8% | 1.9% |
| Grace City | 52 | −3.7% | 1.6% |
4 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).
Foster County, Homes
Homes in Foster County
Foster County is a place of houses on their own lots: 82% of its 1,782 homes are detached single-family houses, against 57% across North Dakota. The homes are older than North Dakota's as a whole: half were built before 1971 (1981 for North Dakota), and 33% date from before 1960. Owners live in 77% of the occupied homes (North Dakota: 63%), so for most households a test and a fix are their own to order.
| Homes | Foster County | North Dakota |
|---|---|---|
| Housing units | 1,782 | 374,866 |
| Detached houses | 82% | 57% |
| In buildings of 5 or more | 6% | 25% |
| Mobile homes | 3% | 7% |
| Built before 1960 | 33% | 24% |
| Built since 2000 | 19% | 31% |
| Middle year built | 1971 | 1981 |
| Owner-occupied | 77% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.