Test results in Williams County
| Result | Share | EPA guidance |
|---|---|---|
| Below 2 pCi/L | 34% | Below EPA's levels |
| 2 to 4 pCi/L | 32% | Consider fixing |
| 4 pCi/L or more | 34% | EPA recommends fixing |
What the data shows
- Higher share of high results than 2 of 53 North Dakota counties.
- Below the North Dakota rate of 59%.
- Lowest of 7 neighbouring counties.
- 66% of results at or above 2 pCi/L.
- EPA's 1993 map: Zone 1, an average above 4 pCi/L. Measured average: 3.6 pCi/L.
- 10.0 tests per 1,000 homes (North Dakota: 17.5).
- Median result 2.9 pCi/L: between the 2 and 4 pCi/L EPA levels.
How Williams County compares
Data table
| Area | Tests ≥ 4 pCi/L | Tests |
|---|---|---|
| Roosevelt County, Montana | 94% | 16 |
| Richland County, Montana | 79% | 42 |
| Sheridan County, Montana | 76% | 70 |
| Mountrail County | 67% | 48 |
| Burke County | 64% | 11 |
| McKenzie County | 56% | 41 |
| Divide County | 50% | 14 |
| Williams County | 34% | 204 |
| North Dakota (53 counties) | 59% | 6,607 |
Same source as Williams County.
What it means for your home
About 1 in 3 results in Williams County were at or above 4 pCi/L, where the EPA recommends a fix. Only a test shows your own home's level.
Levels in pCi/L from the EPA. The WHO reference level is 100 Bq/m³, about 2.7 pCi/L.
Test your home
Start with a short-term test (2–90 days) and confirm a result of 4 pCi/L or more with a second test. EPA guide
Sponsored: we earn a commission on purchases through these links. We haven't tested Airthings monitors yet.
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Fixing high radon
No local job records yet. National range: $800–$2,500, average $1,200 (EPA, 2003). Cost guide →
About this data
Source: Radon test results from laboratories (CDC Environmental Public Health Tracking Network). Period: 2008–2017. Tests: 204. Read the methodology →
These are voluntary and real-estate tests, not a random sample of homes, so they describe tested homes rather than every home.
About this page
Published by Ray Roman, editor of Radon by County. Figures are loaded from the cited source and spot-checked against it. Editorial policy · About us