🔍

US Radon Zone Map

The EPA classifies every US county into one of three radon zones based on predicted average indoor radon levels. The map below shows the predominant radon zone for each state — the zone classification held by the majority of its counties.

Nationally, 1074 counties are Zone 1 (highest risk), 1034 are Zone 2 (moderate), and 1035 are Zone 3 (lowest). Click any state to see county-level detail.

Zone 1 Highest risk (>4 pCi/L) Zone 2 Moderate (2–4 pCi/L) Zone 3 Lowest (<2 pCi/L)
Alaska Zone 3Alabama Zone 2Arkansas Zone 3Arizona Zone 2California Zone 2Colorado Zone 1Connecticut Zone 1Delaware Zone 3Florida Zone 3Georgia Zone 3Hawaii Zone 3Iowa Zone 1Idaho Zone 2Illinois Zone 1Indiana Zone 1Kansas Zone 1Kentucky Zone 2Louisiana Zone 3Massachusetts Zone 2Maryland Zone 2Maine Zone 1Michigan Zone 3Minnesota Zone 1Missouri Zone 2Mississippi Zone 3Montana Zone 1North Carolina Zone 3North Dakota Zone 1Nebraska Zone 1New Hampshire Zone 2New Jersey Zone 2New Mexico Zone 2Nevada Zone 1New York Zone 1Ohio Zone 1Oklahoma Zone 3Oregon Zone 2Pennsylvania Zone 1Rhode Island Zone 1South Carolina Zone 3South Dakota Zone 1Tennessee Zone 1Texas Zone 3Utah Zone 2Virginia Zone 1Vermont Zone 2Washington Zone 3Wisconsin Zone 2West Virginia Zone 2Wyoming Zone 1

Understanding the EPA Radon Zone Map

The EPA's Map of Radon Zones was developed in the early 1990s to help state and local governments target resources for radon risk reduction. The map assigns each of the 3,143 US counties to one of three zones based on predicted average indoor radon screening levels:

What Drives Radon Levels

Radon comes from the natural decay of uranium in soil and rock. The concentration of radon that accumulates indoors depends on the local geology (granite, shale, and phosphate deposits produce more radon), soil permeability (loose soils let radon move more easily), home construction (cracks, gaps, and sump pits), and ventilation patterns.

The EPA zone map uses a combination of indoor radon measurements, geology, aerial radioactivity surveys, soil permeability data, and building construction information. It represents county-level averages — individual homes within any zone can have radon levels that differ significantly from the predicted average.

Why Zone Doesn't Tell the Whole Story

A Zone 3 classification doesn't mean your home is safe. Elevated radon has been found in homes in every state and in all three zones. Conversely, many homes in Zone 1 counties test well below the EPA action level. The zone map is a tool for assessing general risk — not a substitute for testing your own home. A short-term radon test kit costs $15–$30 and takes less than a week.

Look Up Your County →