Median AQI
45
Good
Indiana · County air quality · 2025
Allen County, Indiana
Median AQI 45 (Good). 58.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 45
- Median AQI
- 58.2%
- Good-air days
- 0
- Unhealthy days
- 12%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Allen County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 45 with 58.2% of 273 monitored days in the Good band, driven mainly by Ozone.
- 45
- median AQI · Good
- 58.2%
- days rated Good
- Ozone
- main pollutant
- 12%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 115.
Data updated July 2026
- Good · 159 d · 58.2%
- Moderate · 111 d · 40.7%
- USG · 3 d · 1.1%
How did Allen County's air break down in 2025?
Across 273 monitored days, 159 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). 273 days monitored. Median AQI: 45 (Good).
Insights: Allen County, Indiana. EPA monitors recorded a median Air Quality Index of 45 across 273 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 159 (58%) fell in the Good band (AQI 0–50), 111 (41%) registered Moderate readings, and 3 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 69, while the worst single-day peak hit 115 (USG). Residents averaged about 17.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (139 days), PM2.5 (134 days). Across the 2020–2025 trend window, good days shifted by -73 and the median AQI moved +0 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 115, usg but never Unhealthy. Nearby counties show comparable readings: Bartholomew (69.2% good, AQI 44); Boone (86.9% good, AQI 38); Brown (94.5% good, AQI 37); Carroll (87.8% good, AQI 37); Clark (59.7% good, AQI 46); Delaware (63.4% good, AQI 44).
Air Quality Summary
Good Days
58.2%
159 of 273 monitored days
-16.8pp vs 75% target
Max AQI Recorded
115
USG
Health Grade
Moderate
90th-pct AQI 69
Allen County, Good days share 58.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Allen 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 273 monitored days across EPA AQI categories.
Good
159
58%
Moderate
111
41%
USG
3
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 Allen County.
- Ozone · 139 days · 50.9%
- PM2.5 · 134 days · 49.1%
Health Impact Assessment
Moderate
Allen County's air quality is rated Moderate based on 58.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 58.2% of monitored days in 2025, with a median AQI of 45. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 139 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Allen County. Best year: 2022 (326 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 232 | 132 | 2 | 0 | 45 | 120 |
| 2021 | 257 | 108 | 0 | 0 | 40 | 100 |
| 2022 | 326 | 23 | 2 | 0 | 35 | 115 |
| 2023 | 267 | 89 | 5 | 0 | 42 | 129 |
| 2024 | 229 | 137 | 0 | 0 | 45 | 100 |
| 2025 | 159 | 111 | 3 | 0 | 45 | 115 |
How does Allen County compare?
How Allen County compares
Good-day share worse than US avg
Allen County 58.2%
Bartholomew County, Indiana 69.2%
US average 76.5%
Median AQI worse than US avg
Allen County 45
Bartholomew County, Indiana 44
US average 38
Unhealthy days / yr about average
Allen County 0
Bartholomew County, Indiana 0
US average 0
Other Counties in Indiana
Air quality comparison for nearby counties in Indiana.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Allen County.
Adair County, Oklahoma
AQI 45 · 59.2% good
Atascosa County, Texas
AQI 45 · 58.0% good
Baker County, Florida
AQI 45 · 69.1% good
Carson City County, Nevada
AQI 45 · 79.3% good
Clinton County, Iowa
AQI 45 · 59.9% good
Comanche County, Oklahoma
AQI 45 · 63.8% good
What Allen 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 45 means for exposure. Health guidance
- See how Allen County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Allen County with its Indiana neighbours before drawing a conclusion about the region. All of Indiana
Based on 273 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 Allen County, Indiana? ▼
Allen County has a median Air Quality Index (AQI) of 45, rated "Good." 58.2% of monitored days (159 out of 273) had good air quality in 2025.
What is the main pollutant in Allen County? ▼
The primary pollutant in Allen County is Ozone (O3), which was the main AQI driver on 139 days (51% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Allen County have? ▼
In 2025, Allen County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 115.
Is the air quality in Allen County getting better or worse? ▼
Air quality in Allen County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 326 good days. Worst year: 2025 with 159 good days.
What does AQI 45 mean for health? ▼
Allen County's median AQI of 45 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 Allen County compare to other counties in Indiana? ▼
Allen County has 58.2% good air days. Nearby counties in Indiana: Bartholomew (69.2% good), Boone (86.9% good), Brown (94.5% good), Carroll (87.8% good), Clark (59.7% good), Delaware (63.4% good).
What is the 90th percentile AQI in Allen County? ▼
The 90th percentile AQI for Allen County is 69, 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.