Clark County, MO radon potential

EPA places Clark 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. Nationally, Clark County ranks higher in radon potential than 37% of rated counties (the 37th percentile).

How Clark County compares

Clark County, Missouri is home to about 6,623 people across 504.606 square miles. Population density there runs about 13 people per square mile. Within its own EPA zone, Clark County is bigger by population than 12% of the counties that share it. Clark County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Clark County's Zone 2 prediction. Clark County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

If Clark County tests above the action level

A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.

Find Missouri's state radon program

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

Where Clark County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Clark County's numbers. Whatever zone Clark County carries, the zone explainer covers what it does and doesn't tell you about any one house.