Lewis and Clark County, MT radon potential

EPA's own radon map rates Lewis and Clark County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Rank it against the rest of the country and Lewis and Clark County lands in the 92nd percentile for radon potential.

How Lewis and Clark County compares

Lewis and Clark County, Montana is home to about 75,129 people across 3,458.38 square miles. Averaged across its land area, Lewis and Clark County runs about 22 people per square mile. Within its own EPA zone, Lewis and Clark County is bigger by population than 78% of the counties that share it. Lewis and Clark County falls in EPA Radon Region 8, one of 291 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Lewis and Clark County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Some Lewis and Clark County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Testing and mitigation in Lewis and Clark County

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 Montana's state radon program

For Lewis and Clark County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Lewis and Clark 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 Lewis and Clark County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Lewis and Clark County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.