Broomfield County, CO: EPA's radon zone, explained
Broomfield County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Broomfield County in the 93rd percentile nationally for radon potential — higher than 93% of the counties EPA has rated.
How Broomfield County compares
Broomfield County, Colorado is home to about 78,323 people across 32.967 square miles. Population density there runs about 2,376 people per square mile. By population, Broomfield County is the 231st largest of every county sharing its EPA zone — the 78th percentile by population within that zone. Broomfield County falls in EPA Radon Region 8, one of 291 counties nationally EPA assigns to that same geologic province.
Zone vs. an actual test
Broomfield County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. Being in Zone 1 raises the odds Broomfield County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.
Testing and mitigation in Broomfield County
For a Broomfield County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.
Find Colorado's state radon program
For Broomfield County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Broomfield 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 Broomfield County's figures come from
The methodology guide shows exactly which EPA and Census sources feed Broomfield County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.