Is Carroll County, MD a radon risk area?

EPA places Carroll 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 97th percentile for radon potential — Carroll County outranks 97% of every county EPA has rated.

Where Carroll County sits nationally

About 177,108 people live in Carroll County, Maryland, spread over 447.615 square miles. Population density there runs about 396 people per square mile. Rank 107 by population within its EPA zone puts Carroll County at the 90th percentile among zone peers. Geologically, Carroll County is grouped into EPA Region 3 alongside 244 other counties that share its rock and soil setting.

What this actually means for a house in Carroll County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Carroll County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Carroll County specifically.

Testing and mitigation in Carroll County

Nothing about Carroll County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Maryland's state radon program

Carroll County's test kit answers today; a Airthings radon monitor keeps answering for Carroll County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

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