Short-term kit
Radon Short Term Test Kit short-term charcoal radon test kit, lab fee included
- Lab fee included
Method: Charcoal
In home: 2 to 7 days
Locations and reports
Radon Levels in Grand Isle County, Vermont
EPA puts Grand Isle County in Zone 3, its lowest radon zone, and only 20 radon tests from it are on file with CDC (2023). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
8.3%
11.1 pts below VT
- Grand Isle
- 8.3%
- Vermont
- 19.4%
72 tests, 2022
Median result
1.6pCi/L
Below action level
- Grand Isle
- 1.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2022
Tests reported
72
13th of 13 by tests
- Grand Isle
- 72
- Chittenden
- 1,260
Reported to CDC before any fix, 2022
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Rank in Vermont
13 of 13
Lowest quarter
- Grand Isle
- 8.3%
- Orange
- 34.0%
By share, of 13 with 30+ tests
Read a result for Grand Isle County
Starts at Grand Isle County's median, 1.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.6 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. Grand Isle County's median reported result, 2022.
The data
Grand Isle County, At a glance
Grand Isle County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Grand Isle County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 12.1% |
| 2015 | 50.0% |
| 2016 | 20.0% |
| 2017 | 17.6% |
| 2018 | 25.0% |
| 2019 | 15.8% |
| 2020 | 21.6% |
| 2021 | 32.3% |
| 2022 | 8.3% |
| 2023 | 30.0% |
2023: 30.0%. Across these years the share ran from 8.3% to 50.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 20 tests were reported to CDC for Grand Isle County over 2023, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Grand Isle County, Compared
Grand Isle County radon figures, compared
Calculated by Radon411Grand Isle County reports fewer high tests than Vermont overall. 8.3% of its 72 tests in 2022 were at or above 4 pCi/L. That is 11.1 points below the 19.4% pooled from 14 Vermont counties.
The newest figure, in 2023, counts only 20 tests (30.0% at or above 4 pCi/L), too few to compare, so this reading uses the 72-test figure.
Ordered from highest share down, it comes 13th of 13 Vermont counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 23.9%; Grand Isle County sits 15.6 points below it.
Next door, the shares run from 0.0% in Clinton County, NY to 14.9% in Franklin County, with Clinton County, NY below Grand Isle County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 8.3% share point the same way here.
Half the tests came in under 1.6 pCi/L and half over it; the single highest reached 9.5 pCi/L. The rest split 62.5% under 2 pCi/L and 29.2% from 2 to 4 (Vermont: 55.8% and 24.9%). Year by year, 2014 opened at 12.1% and 2022 closed at 8.3% (down 3.8 points), with 2021 the high at 32.3%.
The busiest year on file was 2022, with 72 tests reported; the quietest, 2015, had 12.
Grand Isle CountyVermont, pooled
8.3% % of tests19.4% % of tests
| Year | Tests | Grand Isle County, at or above 4 pCi/L | Vermont, pooled |
|---|---|---|---|
| 2014 | 33 | 12.1% | 18.3% |
| 2017 | 51 | 17.6% | 16.4% |
| 2018 | 40 | 25.0% | 15.8% |
| 2019 | 38 | 15.8% | 14.3% |
| 2020 | 37 | 21.6% | 16.5% |
| 2021 | 31 | 32.3% | 19.2% |
| 2022 | 72 | 8.3% | 19.4% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Grand Isle County, Geology
The ground under Grand Isle County
PredictedMost of the ground under Grand Isle County is one class on USGS's geologic map: 99.9% of its land is low radon potential, with 0.1% moderate. All of it lies in the area the map calls Champlain Lowland, to which USGS gives a radon index of 8, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Champlain Lowland | Cambrian-Ordovician sedimentary rocks with little or low-grade metamorphism. | Low | 8 | 99.9% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Grand Isle County beside the ground around it
Vermont as a whole has more moderate-potential ground than Grand Isle County: 87.8% of its land, against 0.1% here. Every one of the 3 counties that border it has more moderate-potential ground, Franklin County the most at 68.1%.
The map rates the ground, not the air in any home.
Local help
Grand Isle County, Local resources
Radon testing and mitigation in Grand Isle County
- Radon ProgramRadon Program, run by Vermont Department of Health, offers free or discounted test kits, and answers questions about testing and mitigation in Vermont.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Join the Department of Health Lab's study on radon in water to receive free test kits for your well or spring.
- Compare kits
- See the Vermont directoryNo professionals are listed in Vermont yet. The state program can point you to registered testers and mitigators.
What Vermont's program says
- Phone
- 802-863-7220
What it means
Grand Isle County, Questions
Questions about radon in Grand Isle County
Are radon levels high in Grand Isle County?
In 2023, 30.0% of the radon tests reported to CDC for Grand Isle County, Vermont were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.5 pCi/L. Of 13 Vermont counties with 30 or more tests for the same period, 12 reported a higher share; pooled, the state comes to 19.4%.
Which counties border Grand Isle County?
Grand Isle County borders 3 counties: Clinton County, NY, Franklin County, VT and Chittenden County, VT.
Products
Grand Isle County, Products
Testing a home in Grand Isle County
In Grand Isle County, 8.3% of 72 tests reported to CDC in 2022 reached 4 pCi/L, against 19.4% pooled across Vermont. 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 Grand Isle County.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Monitor
EcoBlu plug-in digital radon monitor with a display
- C-NRPP 2024/25: Not included
- Plug-in
- Alarm
- Screen
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Grand Isle County, Bordering counties
Counties bordering Grand Isle County
Calculated by Radon411- Radon levels in Franklin County, VTEPA zone 2
14.9%at or above 4 pCi/L
Median 1.2 pCi/L · 141 tests · 6.6 points above Grand Isle County
- Radon levels in Chittenden County, VTEPA zone 3
12.1%at or above 4 pCi/L
Median 1.4 pCi/L · 1,260 tests · 3.8 points above Grand Isle County
- Radon levels in Clinton County, NYEPA zone 2
0.0%at or above 4 pCi/L
Median 0.3 pCi/L · 48 tests · 8.3 points below Grand Isle County
Grand Isle County, Cities and towns
Cities and towns in Grand Isle County
The Census Bureau estimates 7,511 residents in Grand Isle County for July 1, 2025, 234 more than in 2020 (+3.2%). That works out to 92 people per square mile of land. Alburgh, its one incorporated place, has 606 residents, 8.1% of the total. Testing is reported here more often than across the state: CDC's 72 reported tests for 2022 come to 9.6 for every 1,000 residents (2025 estimate), against 6.3 for Vermont.
Alburgh is the one incorporated place here; CDC publishes no figure by town, so it reads Grand Isle County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Alburgh | 606 | +2.0% | 8.1% |
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).
Grand Isle County, Homes
Homes in Grand Isle County
Grand Isle County is a place of houses on their own lots: 83% of its 5,301 homes are detached single-family houses, against 67% across Vermont. Half of its homes were built before 1982, close to Vermont's 1976: 26% date from before 1960 and 25% from 2000 or later. Owners live in 91% of the occupied homes (Vermont: 73%), so for most households a test and a fix are their own to order.
| Homes | Grand Isle County | Vermont |
|---|---|---|
| Housing units | 5,301 | 337,072 |
| Detached houses | 83% | 67% |
| In buildings of 5 or more | 1% | 11% |
| Mobile homes | 13% | 6% |
| Built before 1960 | 26% | 33% |
| Built since 2000 | 25% | 17% |
| Middle year built | 1982 | 1976 |
| Owner-occupied | 91% | 73% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.