Glossary · Health & indoor air
EPA radon zone
Also called: radon zone · EPA zone 1 · EPA zone 2 · EPA zone 3 · Map of Radon Zones
EPA's 1993 county map of radon potential, from Zone 1 (highest) to Zone 3 (lowest); EPA says not to use it to decide whether to test.
What it means
Zone 1 counties have the highest potential, with predicted average indoor levels that may exceed 4 pCi/L; Zone 2 is moderate (2 to 4 pCi/L) and Zone 3 low (under 2 pCi/L). The map was made to help put radon-resistant building codes in place, and homes with high radon have been found in all three zones.
Why it matters in an audit
A low zone doesn't make your house safe, so treat the zone as background and rely on a test of your own home.
Typical numbers
Reference values with their sources. Your auditor’s report gives the figure for your own house.