Marshall County, WV radon potential

EPA's own radon map rates Marshall County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. That puts Marshall County in the 85th percentile nationally for radon potential — higher than 85% of the counties EPA has rated.

Where Marshall County sits nationally

Marshall County, West Virginia is home to about 29,354 people across 305.396 square miles. Averaged across its land area, Marshall County runs about 96 people per square mile. Within its own EPA zone, Marshall County is bigger by population than 56% of the counties that share it. Marshall County falls in EPA Radon Region 3, one of 245 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Marshall County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. That doesn't mean every Marshall County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

If Marshall 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 West Virginia's state radon program

For Marshall County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Marshall 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 Marshall 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.