EPA Map of Radon Zones · state summary
Where indoor radon runs highest in the US
The EPA publishes a three-tier county-level Map of Radon Zones based on average screening measurements: Zone 1 averages 4 pCi/L or higher (above the EPA action level), Zone 2 averages 2-4 pCi/L, and Zone 3 averages below 2 pCi/L. This page summarizes the dominant zone per state. Click any state for local pricing + certified mitigators.
Zone 1 — highest indoor radon (≥ 4 pCi/L avg)
EPA recommends testing and mitigation if levels exceed 4 pCi/L. Most homes in these states benefit from a baseline test. · Zone 1 (highest — avg ≥ 4 pCi/L)
Zone 2 — moderate (2-4 pCi/L avg)
Mitigation is voluntary in this range; the EPA suggests considering action especially if a long-term test confirms levels above 2 pCi/L. · Zone 2 (moderate — 2-4 pCi/L)
Zone 3 — low (< 2 pCi/L avg)
Most counties in these states test below the action level on average, but individual home readings vary. Testing is still recommended before sale or major renovation. · Zone 3 (low — < 2 pCi/L)