Grant County, SD radon potential

EPA's own radon map rates Grant County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Grant County sits at the 74th percentile nationally for radon potential — above 74 of every 100 rated counties.

How Grant County compares

Grant County, South Dakota is home to about 7,618 people across 681.446 square miles. Averaged across its land area, Grant County runs about 11 people per square mile. Within its own EPA zone, Grant County is bigger by population than 22% of the counties that share it. Grant 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

Grant 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 Grant 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.

Next steps for a home in Grant 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 South Dakota's state radon program

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

Grant County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.