Radon risk varies significantly across the United States. While every state has areas with elevated radon, some states consistently show higher average indoor radon levels than others. Here's a state-by-state overview to help you understand your regional risk.
Highest Radon Risk States (EPA Zone 1)
The following states have the highest proportion of counties in EPA Zone 1, where predicted average indoor radon levels exceed 4 pCi/L:
- Iowa — The highest average radon levels in the U.S. Nearly all counties are in Zone 1.
- Minnesota — High radon levels statewide, particularly in the north.
- North Dakota — Uranium-rich geology drives high radon concentrations.
- South Dakota — Similar geology to North Dakota with widespread high-risk areas.
- Pennsylvania — Significant radon problem, especially in the central and eastern regions.
- Montana — Large Zone 1 areas due to granite and uranium-bearing rock.
- Colorado — High elevation and uranium-rich soils contribute to elevated levels.
- Idaho — Widespread high-risk zones across the state.
- Wyoming — Uranium mining history reflects the region's naturally high radon potential.
- Ohio, Indiana, Wisconsin — Significant Zone 1 coverage in the Midwest.
Moderate Radon Risk States (EPA Zone 2)
Many states fall primarily in Zone 2, with predicted average levels between 2 and 4 pCi/L. These include much of the Southeast, Mid-Atlantic, and Pacific Northwest. Testing is still strongly recommended in these areas.
Lower Radon Risk States (EPA Zone 3)
States like Hawaii, Louisiana, and parts of Florida and Texas have more Zone 3 counties. However, individual homes in these states can still have elevated radon levels due to local geology and building construction.
The Most Important Point
Radon zone maps show predicted averages — not guarantees. A home in a Zone 3 state can have radon levels above 10 pCi/L, while a home in a Zone 1 state might test below 2 pCi/L. The only way to know your home's radon level is to test it.
Know Your Home's Radon Level — Regardless of Your State
The GZAIR Radon Detector gives you real-time radon data specific to your home — because state averages can't tell you what's happening in your basement.
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