Median AQI
54
Moderate
Colorado · County air quality · 2025
Denver County, Colorado
Median AQI 54 (Moderate). 44.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 54
- Median AQI
- 44.2%
- Good-air days
- 0
- Unhealthy days
- 5%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Denver County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 54 with 44.2% of 274 monitored days in the Good band, driven mainly by Ozone.
- 54
- median AQI · Moderate
- 44.2%
- days rated Good
- Ozone
- main pollutant
- 5%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 115.
Data updated July 2026
- Good · 121 d · 44.2%
- Moderate · 147 d · 53.6%
- USG · 6 d · 2.2%
How did Denver County's air break down in 2025?
Across 274 monitored days, 121 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 115 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 274 days monitored. Median AQI: 54 (Moderate).
Insights: Denver County, Colorado. EPA monitors recorded a median Air Quality Index of 54 across 274 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 121 (44%) fell in the Good band (AQI 0–50), 147 (54%) registered Moderate readings, and 6 (2%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 77, while the worst single-day peak hit 115 (USG). Residents averaged about 13.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (161 days), PM2.5 (82 days), NO2 (30 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -16 and the median AQI moved +1 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 115, usg but never Unhealthy. Nearby counties show comparable readings: Adams (50.2% good, AQI 50); Alamosa (90.8% good, AQI 24); Arapahoe (47.3% good, AQI 51); Archuleta (79.5% good, AQI 32); Boulder (50.9% good, AQI 50); Clear Creek (64.4% good, AQI 48).
Air Quality Summary
Good Days
44.2%
121 of 274 monitored days
-30.8pp vs 75% target
Max AQI Recorded
115
USG
Health Grade
Poor
90th-pct AQI 77
Denver County, Good days share 44.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Denver County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 274 monitored days across EPA AQI categories.
Good
121
44%
Moderate
147
54%
USG
6
2%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Denver County.
- Ozone · 161 days · 58.8%
- PM2.5 · 82 days · 29.9%
- NO₂ · 30 days · 10.9%
- CO · 1 days · 0.4%
Health Impact Assessment
Poor
Denver County's air quality is rated Poor based on 44.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 44.2% of monitored days in 2025, with a median AQI of 54. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 161 of 274 monitored days.
5-Year Air Quality Trend
Air quality is improving in Denver County. Best year: 2022 (161 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 137 | 212 | 17 | 0 | 53 | 150 |
| 2021 | 128 | 202 | 31 | 4 | 55 | 166 |
| 2022 | 161 | 197 | 7 | 0 | 52 | 112 |
| 2023 | 131 | 228 | 4 | 2 | 54 | 179 |
| 2024 | 129 | 208 | 26 | 3 | 55 | 172 |
| 2025 | 121 | 147 | 6 | 0 | 54 | 115 |
How does Denver County compare?
How Denver County compares
Good-day share worse than US avg
Denver County 44.2%
Adams County, Colorado 50.2%
US average 76.5%
Median AQI worse than US avg
Denver County 54
Adams County, Colorado 50
US average 38
Unhealthy days / yr about average
Denver County 0
Adams County, Colorado 0
US average 0
Other Counties in Colorado
Air quality comparison for nearby counties in Colorado.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Denver County.
Franklin County, Ohio
AQI 54 · 39.8% good
Fresno County, California
AQI 54 · 40.1% good
Hamilton County, Ohio
AQI 54 · 32.1% good
Hidalgo County, Texas
AQI 54 · 36.2% good
Inyo County, California
AQI 54 · 40.7% good
Larimer County, Colorado
AQI 54 · 40.1% good
What Denver County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 54 means for exposure. Health guidance
- See how Denver County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Denver County with its Colorado neighbours before drawing a conclusion about the region. All of Colorado
Based on 274 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Denver County, Colorado? ▼
Denver County has a median Air Quality Index (AQI) of 54, rated "Moderate." 44.2% of monitored days (121 out of 274) had good air quality in 2025.
What is the main pollutant in Denver County? ▼
The primary pollutant in Denver County is Ozone (O3), which was the main AQI driver on 161 days (59% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Denver County have? ▼
In 2025, Denver County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 115.
Is the air quality in Denver County getting better or worse? ▼
Air quality in Denver County is improving based on 5-year trends (2020-2025). Best year: 2022 with 161 good days. Worst year: 2025 with 121 good days.
What does AQI 54 mean for health? ▼
Denver County's median AQI of 54 falls in the "Moderate" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Denver County compare to other counties in Colorado? ▼
Denver County has 44.2% good air days. Nearby counties in Colorado: Adams (50.2% good), Alamosa (90.8% good), Arapahoe (47.3% good), Archuleta (79.5% good), Boulder (50.9% good), Clear Creek (64.4% good).
What is the 90th percentile AQI in Denver County? ▼
The 90th percentile AQI for Denver County is 77, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 115 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.