Radon · Colorado
Radon in Colorado
Of the 10 Colorado ZIPs zipradar carries, 9 sit in EPA Radon Zone 1 (highest predicted potential, above 4 pCi/L), 1 in Zone 2 (moderate, 2–4 pCi/L). The zone is a county-level EPA prediction, not a reading from any building — it narrows the question but does not settle it, and EPA's own guidance is that the only way to know a specific home is an at-home test kit.
Last verified 2026-09-24 · methodology
Radon by ZIP code in Colorado
EPA's county radon zone for each ZIP zipradar covers. Tap a ZIP for what the zone means and how to test.
| ZIP | EPA radon zone |
|---|---|
| 80202DenverDenver County | Zone 1 · highest |
| 80206Denver (Cherry Creek)Denver County | Zone 1 · highest |
| 80424BreckenridgeSummit County | Zone 1 · highest |
| 80302BoulderBoulder County | Zone 1 · highest |
| 81611AspenPitkin County | Zone 1 · highest |
| 80525Fort CollinsLarimer County | Zone 1 · highest |
| 81301DurangoLa Plata County | Zone 2 · moderate |
| 80205Denver (Five Points)Denver County | Zone 1 · highest |
| 80113Englewood (CO)Arapahoe County | Zone 1 · highest |
| 80020Broomfield (CO)Broomfield County | Zone 1 · highest |
County-level figures from EPA Radon Zones, joined to each ZIP by county. None of them is a measurement at a specific address.
What lands here
Pages show the county zone, what the classification means for home testing recommendations, and state-level supplementary data where available.
Source & refresh
EPA Radon Zones. Refreshed static 1993 baseline plus state-level supplementary updates. Primary source →
Colorado top concern
Radon Zone 1, wildfire on the Front Range
Colorado is one of the most uniformly Zone 1 radon states in the US. WUI wildfire risk concentrates along the Front Range from Boulder to Colorado Springs. Drinking water sourcing splits between Front Range water districts and Western Slope reclamation projects, each with distinct EPA SDWIS compliance histories.
See Colorado state page for the full state-level rollup across all 12 dimensions.
Read more on radon
Editorial deep-dives explaining the source data, its limits, and how to read it.
EPA Radon Zones — what 1, 2, and 3 mean and when you should test
EPA classifies every US county into Zone 1 (high), Zone 2 (moderate), or Zone 3 (low) for radon. Plain-English guide to the classifications and at-home testing.
EPA SDWIS — how to read drinking-water violations and what they actually mean
Plain-English guide to EPA SDWIS drinking-water violations: health-based vs. monitoring vs. reporting violations, MCLs, and what triggers a public notice.
Radon and real estate — what disclosure laws and home tests actually require
What home sellers must disclose about radon by state, when home tests are required, and how to interpret radon-mitigation systems if a home you're buying has one.
Radon disclosure during real-estate transactions — state-by-state
Whether sellers must disclose known radon results varies by state. Quick map of mandatory-disclosure states + what to ask for during inspection.