EPA radon zones by county

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Zone 1 · above 4 pCi/L predictedZone 2 · 2–4 pCi/LZone 3 · under 2 pCi/L

Radon zones explained

EPA’s Map of Radon Zones puts every county in one of three zones by its predicted average indoor radon level. 13,575 ZIP codes are in zone 1, 13,721 in zone 2 and 12,577 in zone 3.

The three zones

Zone 1 — predicted average above 4 pCi/L (highest potential). Zone 2 — 2 to 4 pCi/L. Zone 3 — under 2 pCi/L. The zones come from indoor measurements, geology, soil permeability and house type; they are meant for planning, not for deciding about a single house.

Test anyway

High radon is found in homes in every zone. EPA and the Surgeon General recommend testing all homes below the third floor. A short-term kit costs about $15–30; if the result is 4 pCi/L or more, EPA recommends a mitigation system (typically $800–2,500).

Source

U.S. EPA, Map of Radon Zones (county list, 2024 version). Look up your ZIP code above for its county’s zone.

What this is — and isn’t. These are records your water utility and state reported to the EPA, and the EPA’s radon map for your county. They describe the system and the area, not the water from your own tap or the air in your home. For that, read your utility’s annual Consumer Confidence Report and test: lead and radon tests are inexpensive.