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 Cascade County, Montana
EPA puts Cascade County in Zone 1, its highest radon zone, and 29.4% of its 235 reported radon tests (2008 to 2017, laboratory totals) 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
29.4%
16.1 pts below MT
- Cascade
- 29.4%
- Montana
- 45.5%
235 tests, 2008 to 2017
Median result
1.7pCi/L
Below action level
- Cascade
- 1.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
235
7th of 23 by tests
- Cascade
- 235
- Missoula
- 2,613
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 Montana
23 of 23
Lowest quarter
- Cascade
- 29.4%
- Richland
- 78.6%
By share, of 23 with 30+ tests
Read a result for Cascade County
Starts at Cascade County's median, 1.7 pCi/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
- 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. Cascade County's median reported result, 2008 to 2017.
The data
Cascade County, At a glance
Cascade County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Cascade County in
USGS geologic potential: High across 97% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Cascade County, 2008 to 2017, laboratory
Under 2 pCi/L: 53%2 to 4 pCi/L: 18%4 pCi/L and above: 29%
Of 235 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 124 | 52.8% |
| 2 to 4 pCi/L | 42 | 17.9% |
| 4 pCi/L and above | 69 | 29.4% |
What these figures count
These are the 235 tests reported to CDC for Cascade 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).
Cascade County, Compared
Cascade County radon figures, compared
Calculated by Radon411Cascade County's 235 reported tests over the 2008 to 2017 laboratory totals had a middle value of 1.7 pCi/L and a maximum of 65.0 pCi/L, and 29.4% reached 4 pCi/L. Montana as a whole (51 Montana counties, pooled) comes to 45.5%: 16.1 points higher than here.
Among its state's counties it ranks 23rd of 23 Montana counties with 30 or more tests for the same period. Statewide for the same period, Richland County reported the highest share (78.6%) and Flathead County the lowest (37.8%).
Below the action level, 124 tests (52.8%) came in under 2 pCi/L, against 29.2% statewide, and 42 tests (17.9%) fell between 2 and 4, against 25.2% statewide. CDC's ten-year totals for Cascade County went from 290 tests (2005 to 2014) to 235 (2008 to 2017), the share going from 34.1% to 29.4%.
EPA's 1993 zone map puts Cascade County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 97% of the county's land high radon potential.
Next door, the shares run from 61.8% in Lewis and Clark County to 64.3% in Judith Basin County.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Cascade County, Geology
The ground under Cascade County
PredictedMost of the ground under Cascade County is one class on USGS's geologic map: 96.9% of its land is high radon potential, with 3.1% moderate. The map puts 86.9% of Cascade County in the area it calls Northern Rocky Mountains and 9.9% in Great Plains (Glaciated), with one smaller area beside them. USGS gives both 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 |
|---|---|---|---|---|
| Northern Rocky Mountains | Granitic, metaigneous, metasedimentary rocks, valley fill colluvium and alluvium. | High | 13 | 86.9% |
| Great Plains (Glaciated) | Glacial deposits derived from Cretaceous shales containing higher than average amounts of uranium. | High | 13 | 9.9% |
| Plains and Mountains | Marine and continental shale, siltstone, and sandstone of Cretaceous and Tertiary ages, and volcanic rocks. | Moderate | 10 | 3.1% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Cascade County beside the ground around it
Cascade County has more high-potential ground than Montana as a whole: 96.9% of its land against 78.5%. Of the 5 counties that border it, 2 have more high-potential ground, Lewis and Clark County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Cascade County, Local resources
Radon testing and mitigation in Cascade County
- Radon Control ProgramRadon Control Program, run by Montana DEQ, does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Montana.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Energy Bureau staff manage the radon information toll-free hotline and distribute subsidized radon test kits to Montana residents.
- Compare kits
- See the Montana directoryNo professionals are listed in Montana yet. The state program can point you to registered testers and mitigators.
What Montana's program says
- Phone
- 1-800-546-0483
- Licensing of radon professionals
Montana DEQ does not certify or require proof of certification for the contractors listed.
What it means
Cascade County, Questions
Questions about radon in Cascade County
Are radon levels high in Cascade County?
Over the 2008 to 2017 laboratory totals, 29.4% of the radon tests reported to CDC for Cascade County, Montana were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.7 pCi/L. Of 23 Montana counties with 30 or more tests for the same period, 22 reported a higher share; pooled, the state comes to 45.5%.
Which counties border Cascade County?
Cascade County borders 5 counties: Teton County, Meagher County, Lewis and Clark County, Chouteau County and Judith Basin County.
Products
Cascade County, Products
Testing a home in Cascade County
In Cascade County, 29.4% of 235 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 45.5% pooled across Montana. In Zone 1 the year-round level in Cascade 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-1085 palm-sized rechargeable radon detector
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
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
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Cascade County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Cascade County
Explore
Cascade County, Bordering counties
Counties bordering Cascade County
Calculated by Radon411- Radon levels in Judith Basin CountyEPA zone 1
64.3%at or above 4 pCi/L
Median 5.9 pCi/L · 42 tests · 34.9 points above Cascade County
- Radon levels in Lewis and Clark CountyEPA zone 1
61.8%at or above 4 pCi/L
Median 5.1 pCi/L · 468 tests · 32.4 points above Cascade County
- Radon levels in Chouteau CountyEPA zone 1
54.5%at or above 4 pCi/L
Median 5.5 pCi/L · 11 tests · 25.1 points above Cascade County
- Radon levels in Teton CountyEPA zone 1
28.6%at or above 4 pCi/L
Median 3.1 pCi/L · 7 tests · 0.8 points below Cascade County
- Radon levels in Meagher CountyEPA zone 1
0.0%at or above 4 pCi/L
Median 3.6 pCi/L · 1 test · 29.4 points below Cascade County
Cascade County, Cities and towns
Cities and towns in Cascade County
The Census Bureau estimates 85,029 residents in Cascade County for July 1, 2025, 619 more than in 2020 (+0.7%). That works out to 32 people per square mile of land. Great Falls alone is home to 60,208 of them, 70.8% of the total. Together its 4 incorporated places hold 72.2% of those residents; the other 27.8% live outside any of them. Reported testing is thin here: 235 tests over 2008 to 2017, or 2.8 for every 1,000 residents (2025 estimate), where Montana as a whole comes to 8.6.
From Great Falls to Neihart, CDC publishes no figure by town: each reads Cascade County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Great Falls | 60,208 | −0.4% | 70.8% |
| Cascade | 577 | −2.4% | 0.7% |
| Belt | 523 | +4.0% | 0.6% |
| Neihart | 41 | −2.4% | Under 0.1% |
Places in Cascade County with a city page: 1 of 1
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).
Cascade County, Homes
Homes in Cascade County
Of Cascade County's 39,248 homes, 67% are detached houses, against 69% across Montana; 13% are in buildings of five or more homes. The homes are older than Montana's as a whole: half were built before 1969 (1980 for Montana), and 37% date from before 1960. 70% of occupied homes are lived in by their owner (Montana: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Cascade County | Montana |
|---|---|---|
| Housing units | 39,248 | 522,939 |
| Detached houses | 67% | 69% |
| In buildings of 5 or more | 13% | 9% |
| Mobile homes | 7% | 10% |
| Built before 1960 | 37% | 26% |
| Built since 2000 | 16% | 27% |
| Middle year built | 1969 | 1980 |
| Owner-occupied | 70% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.