What the three zones mean
- Zone 1: predicted average indoor screening level above 4 pCi/L. The EPA recommends every home be tested and that new homes use radon-resistant construction.
- Zone 2: predicted average between 2 and 4 pCi/L. The EPA recommends every home be tested; about one in three Zone 2 homes still reads at or above the action level.
- Zone 3: predicted average below 2 pCi/L. Testing is still recommended, because individual homes in any county can read high.
The zone is a county-level planning estimate taken straight from the EPA Map of Radon Zones. It is not a measurement of any individual house, and it does not replace a test.
Find your county
Alabama
- Jefferson County Zone 2
- Madison County Zone 1
- Mobile County Zone 3
Arizona
- Maricopa County Zone 2
- Pima County Zone 2
- Pinal County Zone 2
Arkansas
- Pulaski County Zone 3
California
- Los Angeles County Zone 2
- San Diego County Zone 3
- Orange County Zone 3
- Riverside County Zone 2
- San Bernardino County Zone 2
- Santa Clara County Zone 2
- Alameda County Zone 2
- Sacramento County Zone 3
- Contra Costa County Zone 2
- Fresno County Zone 2
- Kern County Zone 2
- Ventura County Zone 1
- San Francisco County Zone 2
- San Joaquin County Zone 3
- San Mateo County Zone 2
- Stanislaus County Zone 3
- Sonoma County Zone 3
- Tulare County Zone 2
- Solano County Zone 3
- Santa Barbara County Zone 1
- Monterey County Zone 2
- Placer County Zone 2
Colorado
- El Paso County Zone 1
- Denver County Zone 1
- Arapahoe County Zone 1
- Jefferson County Zone 1
- Adams County Zone 1
- Douglas County Zone 1
- Larimer County Zone 1
- Weld County Zone 1
Delaware
- New Castle County Zone 2
District of Columbia
- District of Columbia Zone 3
Florida
- Miami-Dade County Zone 2
- Broward County Zone 3
- Palm Beach County Zone 3
- Hillsborough County Zone 2
- Orange County Zone 3
- Duval County Zone 3
- Pinellas County Zone 3
- Lee County Zone 3
- Polk County Zone 2
- Pasco County Zone 3
- Brevard County Zone 3
- Volusia County Zone 3
- Seminole County Zone 3
- Sarasota County Zone 3
- Osceola County Zone 3
- Manatee County Zone 3
- Lake County Zone 3
- Marion County Zone 2
- Collier County Zone 3
- St. Lucie County Zone 3
Georgia
- Fulton County Zone 1
- Gwinnett County Zone 1
- Cobb County Zone 1
- DeKalb County Zone 1
Hawaii
- Honolulu County Zone 3
Idaho
- Ada County Zone 2
Illinois
- Cook County Zone 2
- DuPage County Zone 2
- Lake County Zone 2
- Will County Zone 2
- Kane County Zone 1
Indiana
- Marion County Zone 1
- Lake County Zone 2
- Allen County Zone 1
- Hamilton County Zone 1
Iowa
- Polk County Zone 1
Kansas
- Johnson County Zone 1
- Sedgwick County Zone 2
Kentucky
- Jefferson County Zone 1
Louisiana
- East Baton Rouge Parish Zone 3
- Jefferson Parish Zone 3
Maryland
- Montgomery County Zone 1
- Prince George's County Zone 2
- Anne Arundel County Zone 2
- Baltimore city Zone 2
Massachusetts
- Middlesex County Zone 1
- Worcester County Zone 1
- Essex County Zone 1
- Suffolk County Zone 3
- Norfolk County Zone 2
- Bristol County Zone 2
- Plymouth County Zone 2
- Hampden County Zone 2
Michigan
- Wayne County Zone 3
- Oakland County Zone 2
- Macomb County Zone 3
- Kent County Zone 2
- Genesee County Zone 2
- Washtenaw County Zone 1
Minnesota
- Hennepin County Zone 1
- Ramsey County Zone 1
- Dakota County Zone 1
- Anoka County Zone 2
Missouri
- Jackson County Zone 1
- St. Charles County Zone 2
Nebraska
- Douglas County Zone 1
Nevada
- Clark County Zone 3
- Washoe County Zone 2
New Hampshire
- Hillsborough County Zone 2
New Jersey
- Bergen County Zone 2
- Middlesex County Zone 2
- Essex County Zone 2
- Hudson County Zone 2
- Ocean County Zone 3
- Monmouth County Zone 1
- Union County Zone 2
- Camden County Zone 2
- Passaic County Zone 2
- Morris County Zone 1
- Burlington County Zone 2
- Mercer County Zone 1
New Mexico
- Bernalillo County Zone 1
New York
- Kings County Zone 3
- Queens County Zone 3
- New York County Zone 3
- Suffolk County Zone 3
- Nassau County Zone 3
- Bronx County Zone 3
- Westchester County Zone 3
- Erie County Zone 1
- Monroe County Zone 2
- Richmond County Zone 3
- Onondaga County Zone 1
- Orange County Zone 1
North Carolina
- Wake County Zone 2
- Mecklenburg County Zone 3
- Guilford County Zone 3
- Forsyth County Zone 2
Ohio
- Franklin County Zone 1
- Cuyahoga County Zone 2
- Hamilton County Zone 1
- Summit County Zone 1
- Montgomery County Zone 1
- Lucas County Zone 2
- Butler County Zone 1
- Stark County Zone 1
Oklahoma
- Oklahoma County Zone 3
- Tulsa County Zone 3
Oregon
- Multnomah County Zone 2
- Washington County Zone 2
- Clackamas County Zone 3
- Lane County Zone 3
Pennsylvania
- Philadelphia County Zone 3
- Allegheny County Zone 1
- Montgomery County Zone 1
- Bucks County Zone 1
- Delaware County Zone 1
- Lancaster County Zone 1
- Chester County Zone 1
- York County Zone 1
- Berks County Zone 1
- Lehigh County Zone 1
Rhode Island
- Providence County Zone 2
South Carolina
- Greenville County Zone 1
- Charleston County Zone 3
- Richland County Zone 3
- Horry County Zone 3
Tennessee
- Shelby County Zone 3
- Davidson County Zone 1
- Knox County Zone 1
- Hamilton County Zone 2
- Rutherford County Zone 1
Texas
- Harris County Zone 3
- Dallas County Zone 3
- Tarrant County Zone 3
- Bexar County Zone 3
- Travis County Zone 3
- Collin County Zone 3
- Denton County Zone 3
- Fort Bend County Zone 3
- Hidalgo County Zone 3
- El Paso County Zone 3
- Montgomery County Zone 3
- Williamson County Zone 3
- Cameron County Zone 3
- Brazoria County Zone 3
- Bell County Zone 3
Utah
- Salt Lake County Zone 2
- Utah County Zone 2
- Davis County Zone 2
Virginia
- Prince William County Zone 2
- Loudoun County Zone 2
- Chesterfield County Zone 1
Washington
- King County Zone 3
- Pierce County Zone 3
- Snohomish County Zone 3
- Spokane County Zone 1
- Clark County Zone 1
Wisconsin
- Milwaukee County Zone 2
- Dane County Zone 1
- Waukesha County Zone 1
Not listed?
This index currently covers the 200 most populated US counties. The $9 report covers any US ZIP code, including counties not listed here, using the same EPA county table.
Source
US EPA Map of Radon Zones county classification table (EPA-402-R-93-071 / EPA 402/A-16/001), reported exactly as published. County population from US Census Bureau estimates, 2024 vintage.