Median AQI
47
Good
Utah · County air quality · 2025
Duchesne County, Utah
Median AQI 47 (Good). 59.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 47
- Median AQI
- 59.4%
- Good-air days
- 0
- Unhealthy days
- 14%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Duchesne County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 47 with 59.4% of 303 monitored days in the Good band, driven mainly by Ozone.
- 47
- median AQI · Good
- 59.4%
- days rated Good
- Ozone
- main pollutant
- 14%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 112.
Data updated July 2026
- Good · 180 d · 59.4%
- Moderate · 121 d · 39.9%
- USG · 2 d · 0.7%
How did Duchesne County's air break down in 2025?
Across 303 monitored days, 180 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 112 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 303 days monitored. Median AQI: 47 (Good).
Insights: Duchesne County, Utah. EPA monitors recorded a median Air Quality Index of 47 across 303 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 180 (59%) fell in the Good band (AQI 0–50), 121 (40%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 77, while the worst single-day peak hit 112 (USG). Residents averaged about 17.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (193 days), PM2.5 (90 days), PM10 (20 days). Across the 2020–2025 trend window, good days shifted by -59 and the median AQI moved +1 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 112, usg but never Unhealthy. Nearby counties show comparable readings: Box Elder (60.0% good, AQI 48); Cache (61.2% good, AQI 46); Carbon (62.9% good, AQI 47); Davis (59.5% good, AQI 48); Garfield (100.0% good, AQI 4); Grand (61.7% good, AQI 47).
Air Quality Summary
Good Days
59.4%
180 of 303 monitored days
-15.6pp vs 75% target
Max AQI Recorded
112
USG
Health Grade
Moderate
90th-pct AQI 77
Duchesne County, Good days share 59.4%
National avg
Share of monitored days at AQI 0-50 (Good band).
Duchesne 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 303 monitored days across EPA AQI categories.
Good
180
59%
Moderate
121
40%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Duchesne County.
- Ozone · 193 days · 63.7%
- PM2.5 · 90 days · 29.7%
- PM10 · 20 days · 6.6%
Health Impact Assessment
Moderate
Duchesne County's air quality is rated Moderate based on 59.4% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 59.4% of monitored days in 2025, with a median AQI of 47. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 193 of 303 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Duchesne County. Best year: 2020 (239 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 239 | 122 | 5 | 0 | 46 | 125 |
| 2021 | 220 | 137 | 7 | 1 | 48 | 155 |
| 2022 | 223 | 138 | 3 | 1 | 48 | 177 |
| 2023 | 180 | 151 | 22 | 11 | 51 | 215 |
| 2024 | 225 | 136 | 3 | 2 | 47 | 165 |
| 2025 | 180 | 121 | 2 | 0 | 47 | 112 |
How does Duchesne County compare?
How Duchesne County compares
Good-day share worse than US avg
Duchesne County 59.4%
Box Elder County, Utah 60.0%
US average 76.5%
Median AQI worse than US avg
Duchesne County 47
Box Elder County, Utah 48
US average 38
Unhealthy days / yr about average
Duchesne County 0
Box Elder County, Utah 0
US average 0
Other Counties in Utah
Air quality comparison for nearby counties in Utah.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Duchesne County.
Beaver County, Pennsylvania
AQI 47 · 54.3% good
Bell County, Texas
AQI 47 · 61.3% good
Bowie County, Texas
AQI 47 · 57.3% good
Bronx County, New York
AQI 47 · 56.6% good
Butte County, California
AQI 47 · 66.1% good
Calcasieu County, Louisiana
AQI 47 · 61.5% good
What Duchesne 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 47 means for exposure. Health guidance
- See how Duchesne County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Duchesne County with its Utah neighbours before drawing a conclusion about the region. All of Utah
Based on 303 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 Duchesne County, Utah? ▼
Duchesne County has a median Air Quality Index (AQI) of 47, rated "Good." 59.4% of monitored days (180 out of 303) had good air quality in 2025.
What is the main pollutant in Duchesne County? ▼
The primary pollutant in Duchesne County is Ozone (O3), which was the main AQI driver on 193 days (64% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Duchesne County have? ▼
In 2025, Duchesne County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 112.
Is the air quality in Duchesne County getting better or worse? ▼
Air quality in Duchesne County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 239 good days. Worst year: 2025 with 180 good days.
What does AQI 47 mean for health? ▼
Duchesne County's median AQI of 47 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Duchesne County compare to other counties in Utah? ▼
Duchesne County has 59.4% good air days. Nearby counties in Utah: Box Elder (60.0% good), Cache (61.2% good), Carbon (62.9% good), Davis (59.5% good), Garfield (100.0% good), Grand (61.7% good).
What is the 90th percentile AQI in Duchesne County? ▼
The 90th percentile AQI for Duchesne County is 77, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 112 (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.