Highest Potential: Zone 1 counties have a predicted average indoor radon screening level greater than 4 pCi/L (pico curies per liter) (red zones)

Moderate Potential: Zone 2 counties have a predicted average indoor radon screening level between 2 and 4 pCi/L (orange zones)

Low Potential: Zone 3 counties have a predicted average indoor radon screening level less than 2 pCi/L (yellow zones)