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 Granite County, Montana
EPA puts Granite County in Zone 1, its highest radon zone, and only 8 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
48.8%
Missoula County
- Missoula
- 48.8%
- Ravalli
- 43.7%
2 of 4 neighbours have 30+ tests, 2006 to 2015
Nearest county
43.7%
Ravalli County, 39 miles
- Ravalli
- 43.7%
- Montana
- 47.4%
Share at 4+ pCi/L, 964 tests, 2006 to 2015
Ground above low
100.0%
Level with Montana
- Granite
- 100.0%
- Montana
- 100.0%
Share of land USGS rates moderate or high potential
Tests reported
8
Too few for a share
- Granite
- 8
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Read a result for Granite County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 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.
The data
Granite County, At a glance
Granite County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Granite 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 Granite County, 2008 to 2017, laboratory
CDC holds 8 reported tests for Granite County over the 2008 to 2017 laboratory totals, with a median of 2.1 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Granite County beside the counties around it is how this page reads it.
What these figures count
Only 8 tests were reported to CDC for Granite County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Granite County, Compared
Granite County radon figures, compared
Calculated by Radon411CDC's largest figure for Granite County rests on 8 tests over the 2008 to 2017 laboratory totals, 2 of them at or above 4 pCi/L, so each test moves its share by 12.5 points and no rank or comparison is drawn from it. Results reached as high as 8.6 pCi/L, with a middle value of 2.1 pCi/L.
Of the counties bordering it, 2 have a figure over the 2006 to 2015 laboratory totals: Missoula County reported the largest share at or above 4 pCi/L, 48.8%, and Ravalli County the smallest, 43.7%. Farther out, Silver Bow County (51 miles away) at 68.9%, Jefferson County (67 miles away) at 66.1% and Lewis and Clark County (70 miles away) at 63.5% have figures too. Pooled across 52 Montana counties, 47.4% of reported tests reached that level; across every county in the country with a figure, 36.3%.
Statewide for the same period, Sheridan County reported the highest share (75.7%) and Hill County the lowest (35.0%). EPA's 1993 map puts Granite County in Zone 1, the map's highest label: a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Granite County, Geology
The ground under Granite County
PredictedUSGS's geologic map puts all of Granite County's mapped land in one class: high radon potential. All of it lies in the area the map calls Northern Rocky Mountains, 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 |
|---|---|---|---|---|
| Northern Rocky Mountains | Granitic, metaigneous, metasedimentary rocks, valley fill colluvium and alluvium. | 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.
Granite County beside the ground around it
Granite County has more high-potential ground than Montana as a whole: 100% of its land against 78.5%. Of the 4 counties that border it, none has as large a share of high-potential ground; Deer Lodge County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Granite County, Local resources
Radon testing and mitigation in Granite 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
Granite County, Questions
Questions about radon in Granite County
Are radon levels high in Granite County?
Over the 2008 to 2017 laboratory totals, 25.0% of the radon tests reported to CDC for Granite County, Montana were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.1 pCi/L. Of the counties bordering it, 2 have a figure over the 2006 to 2015 laboratory totals: Missoula County reported the largest share at or above 4 pCi/L, 48.8%, and Ravalli County the smallest, 43.7%.
Which counties border Granite County?
Granite County borders 4 counties: Deer Lodge County, Ravalli County, Powell County and Missoula County.
Products
Granite County, Products
Testing a home in Granite County
No CDC figure names Granite County; the nearest county with one, Ravalli County (39 miles away), reported 43.7% of its tests at or above 4 pCi/L over the 2006 to 2015 laboratory totals, the only reading nearby until a test of this home. In Zone 1 the year-round level in Granite 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
Monitor
RM-65 rechargeable radon detector with a color screen and alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 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
Granite County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Granite County
Explore
Granite County, Bordering counties
Counties bordering Granite County
Calculated by Radon411- Radon levels in Powell CountyEPA zone 1
73.9%at or above 4 pCi/L
Median 8.5 pCi/L · 23 tests
- Radon levels in Missoula CountyEPA zone 1
48.8%at or above 4 pCi/L
Median 3.9 pCi/L · 2,122 tests
- Radon levels in Ravalli CountyEPA zone 1
43.7%at or above 4 pCi/L
Median 3.2 pCi/L · 964 tests
- Radon levels in Deer Lodge CountyEPA zone 1
37.5%at or above 4 pCi/L
Median 3.5 pCi/L · 16 tests
Granite County, Cities and towns
Cities and towns in Granite County
Granite County is growing: the Census Bureau puts it at 3,658 residents on July 1, 2025, up 10.6% from 3,307 in 2020. Spread over its land, that is 2.1 people to the square mile. Its largest town, Philipsburg, has 926 residents, 25.3% of the total. Together its 2 incorporated places hold 33.5% of those residents; the other 66.5% live outside any of them. Reported testing is thin here: 8 tests over 2008 to 2017, or 2.2 for every 1,000 residents (2025 estimate), where Montana as a whole comes to 8.6.
From Philipsburg to Drummond, CDC publishes no figure by town: each reads Granite County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Philipsburg | 926 | +10.4% | 25.3% |
| Drummond | 298 | +10.4% | 8.1% |
2 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).
Granite County, Homes
Homes in Granite County
Granite County is a place of houses on their own lots: 86% of its 2,605 homes are detached single-family houses, against 69% across Montana. Half of its homes were built before 1977, close to Montana's 1980: 34% date from before 1960 and 28% from 2000 or later. Owners live in 76% of the occupied homes (Montana: 69%), so for most households a test and a fix are their own to order.
| Homes | Granite County | Montana |
|---|---|---|
| Housing units | 2,605 | 522,939 |
| Detached houses | 86% | 69% |
| In buildings of 5 or more | under 1% | 9% |
| Mobile homes | 9% | 10% |
| Built before 1960 | 34% | 26% |
| Built since 2000 | 28% | 27% |
| Middle year built | 1977 | 1980 |
| Owner-occupied | 76% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.