Air quality · Colorado
Air quality in Colorado
Across the 8 Colorado ZIPs with EPA county air-quality data, the median day is Good in all 8 (median AQI 19–50). 1 day across those counties reached Unhealthy or worse in 2025. This is a 2025 county annual summary, not a live reading.
Last verified 2026-09-24 · methodology
Air quality by ZIP code in Colorado
EPA's 2025 annual summary for each ZIP's county. Median AQI is the typical day; lower is cleaner.
| ZIP | Median AQI | Good days | Unhealthy or worse |
|---|---|---|---|
| 80202DenverDenver County | 50 Good | 184 of 365 | 0 |
| 80206Denver (Cherry Creek)Denver County | 50 Good | 184 of 365 | 0 |
| 80424BreckenridgeSummit County | No data | ||
| 80302BoulderBoulder County | 48 Good | 213 of 365 | 0 |
| 81611AspenPitkin County | 19 Good | 337 of 365 | 1 |
| 80525Fort CollinsLarimer County | 50 Good | 185 of 365 | 0 |
| 81301DurangoLa Plata County | 48 Good | 222 of 365 | 0 |
| 80205Denver (Five Points)Denver County | 50 Good | 184 of 365 | 0 |
| 80113Englewood (CO)Arapahoe County | 48 Good | 212 of 365 | 0 |
| 80020Broomfield (CO)Broomfield County | No data |
County-level figures from EPA Air Quality System (AQS), annual county summary, joined to each ZIP by county. None of them is a measurement at a specific address.
What lands here
Pages show the 2025 median AQI category (Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, Hazardous) for the ZIP's county, plus the year's max/90th-percentile AQI and day-count breakdown by category.
Source & refresh
EPA Air Quality System (AQS), annual county summary. Refreshed annual (epa aqs publication). 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 air quality
Editorial deep-dives explaining the source data, its limits, and how to read it.
EPA AQI categories explained — what 0–50 Good through 301–500 Hazardous mean
Plain-English guide to the six EPA Air Quality Index categories: 0–50 Good, 51–100 Moderate, 101–150 Unhealthy for Sensitive Groups, 151–200 Unhealthy, 201–300 Very Unhealthy, 301–500 Hazardous — what each level means and who is at risk.
AQI explained — what 50, 100, 150 actually mean for your lungs
Plain-English guide to the EPA Air Quality Index (AQI) and the 6 categories from Good to Hazardous. When to take precautions and which pollutants matter.
Wildfire Hazard Potential — what the USFS scale means and how to defend your home
Plain-English guide to the USDA Forest Service's Wildfire Hazard Potential 1–5 scale, how to read your community's risk, and concrete home-defense measures.
AirNow + wildfire smoke — when AQI is a real-time tool
How EPA AirNow handles real-time wildfire smoke, what the colors mean during fire season, and where AirNow leaves gaps you should know about.