| |
 |
Zone 1 counties have a predicted average indoor radon screening level greater than 4 pCi/L (pico curies per liter) (red zones) | Highest Potential |
 |
Zone 2 counties have a predicted average indoor radon screening level between 2 and 4 pCi/L (orange zones) | Moderate Potential |
 |
Zone 3 counties have a predicted average indoor radon screening level less than 2 pCi/L (yellow zones) | Low Potential |