Carter County, MO: EPA's radon zone, explained

EPA places Carter County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and Carter County lands in the 36th percentile for radon potential.

Carter County by the numbers

Carter County, Missouri is home to about 5,359 people across 507.359 square miles. Population density there runs about 11 people per square mile. By population, Carter County is the 934th largest of every county sharing its EPA zone — the 10th percentile by population within that zone. Carter County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Carter County

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Carter County's Zone 2 prediction lands in the gap between the two. Carter County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

Testing and mitigation in Carter County

For a Carter County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Missouri's state radon program

For Carter County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Carter County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where Carter County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.