Is Billings County, ND a radon risk area?
EPA places Billings 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 66th percentile for radon potential — Billings County outranks 66% of every county EPA has rated.
Billings County by the numbers
About 1,063 people live in Billings County, North Dakota, spread over 1,148.488 square miles. That works out to roughly 1 people per square mile. Rank 1061 by population within its EPA zone puts Billings County at the 0th percentile among zone peers. EPA's geology-based Region 8 groups Billings County with 290 other counties nationally sharing its underlying rock and soil profile.
Zone vs. an actual test
Where the national indoor average runs about 1.3 pCi/L, Billings County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in Billings County will test well under the action level, and EPA's guidance is to test regardless of zone.
Testing and mitigation in Billings County
Nothing about Billings 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 North Dakota's state radon program
Billings County's test kit answers today; a Airthings radon monitor keeps answering for Billings County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.
More on how this number was built
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.