Fremont County, WY radon potential

EPA places Fremont County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally that's the 88th percentile for radon potential — Fremont County outranks 88% of every county EPA has rated.

How Fremont County compares

Fremont County, Wyoming is home to about 39,721 people across 9,183.597 square miles. Averaged across its land area, Fremont County runs about 4 people per square mile. Within its own EPA zone, Fremont County is bigger by population than 64% of the counties that share it. Geologically, Fremont County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.

What this actually means for a house in Fremont County

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Fremont County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. Some Fremont 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.

If Fremont 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 Wyoming's state radon program

For Fremont County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Fremont 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 Fremont 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. Whatever zone Fremont County carries, the zone explainer covers what it does and doesn't tell you about any one house.