EPA Zone Data 2026
California Radon Map, Levels & Testing Guide
View EPA radon zone classifications for every county in California. Open your county to compare basement test meaning, EPA action thresholds, and when mitigation pricing becomes worth checking.
2
Zone 1
High Risk
High Risk
29
Zone 2
Moderate
Moderate
27
Zone 3
Low Risk
Low Risk
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Browse Counties
Jump to the Directory
Open your county to see its EPA zone, testing meaning, and the point where mitigation becomes worth pricing.
Alameda County
Zone 2
Alpine County
Zone 2
Amador County
Zone 2
Calaveras County
Zone 2
Contra Costa County
Zone 2
El Dorado County
Zone 2
Fresno County
Zone 2
Inyo County
Zone 2
Kern County
Zone 2
Los Angeles County
Zone 2
Madera County
Zone 2
Mariposa County
Zone 2
Mono County
Zone 2
Monterey County
Zone 2
Nevada County
Zone 2
Placer County
Zone 2
Plumas County
Zone 2
Riverside County
Zone 2
San Benito County
Zone 2
San Bernardino County
Zone 2
San Francisco County
Zone 2
San Luis Obispo County
Zone 2
San Mateo County
Zone 2
Santa Barbara County
Zone 1
Santa Clara County
Zone 2
Santa Cruz County
Zone 2
Sierra County
Zone 2
Tulare County
Zone 2
Tuolumne County
Zone 2
Ventura County
Zone 1
Yuba County
Zone 2
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