Median AQI
43
Good
Ohio · County air quality · 2025
Allen County, Ohio
Median AQI 43 (Good). 65.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 43
- Median AQI
- 65.9%
- Good-air days
- 0
- Unhealthy days
- 24%
- 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 43 with 65.9% of 296 monitored days in the Good band, driven mainly by PM2.5.
- 43
- median AQI · Good
- 65.9%
- days rated Good
- PM2.5
- main pollutant
- 24%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 129.
Data updated July 2026
- Good · 195 d · 65.9%
- Moderate · 100 d · 33.8%
- USG · 1 d · 0.3%
How did Allen County's air break down in 2025?
Across 296 monitored days, 195 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 129 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 296 days monitored. Median AQI: 43 (Good).
Insights: Allen County, Ohio. EPA monitors recorded a median Air Quality Index of 43 across 296 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 195 (66%) fell in the Good band (AQI 0–50), 100 (34%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 63, while the worst single-day peak hit 129 (USG). Residents averaged about 19.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (149 days), Ozone (147 days). Across the 2020–2025 trend window, good days shifted by -94 and the median AQI moved +3 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 129, usg but never Unhealthy. Nearby counties show comparable readings: Ashtabula (81.2% good, AQI 43); Athens (80.3% good, AQI 33); Belmont (63.0% good, AQI 42); Butler (33.3% good, AQI 55); Clark (59.4% good, AQI 46); Clermont (72.1% good, AQI 43).
Air Quality Summary
Good Days
65.9%
195 of 296 monitored days
-9.1pp vs 75% target
Max AQI Recorded
129
USG
Health Grade
Moderate
90th-pct AQI 63
Allen County, Good days share 65.9%
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 296 monitored days across EPA AQI categories.
Good
195
66%
Moderate
100
34%
USG
1
0%
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.
- PM2.5 · 149 days · 50.3%
- Ozone · 147 days · 49.7%
Health Impact Assessment
Moderate
Allen County's air quality is rated Moderate based on 65.9% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 65.9% of monitored days in 2025, with a median AQI of 43. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 149 of 296 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Allen County. Best year: 2020 (289 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 289 | 70 | 1 | 0 | 40 | 105 |
| 2021 | 260 | 105 | 0 | 0 | 42 | 87 |
| 2022 | 272 | 93 | 0 | 0 | 41 | 97 |
| 2023 | 252 | 105 | 5 | 3 | 44 | 194 |
| 2024 | 275 | 84 | 0 | 0 | 42 | 97 |
| 2025 | 195 | 100 | 1 | 0 | 43 | 129 |
How does Allen County compare?
How Allen County compares
Good-day share worse than US avg
Allen County 65.9%
Ashtabula County, Ohio 81.2%
US average 76.5%
Median AQI worse than US avg
Allen County 43
Ashtabula County, Ohio 43
US average 38
Unhealthy days / yr about average
Allen County 0
Ashtabula County, Ohio 0
US average 0
Other Counties in Ohio
Air quality comparison for nearby counties in Ohio.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Allen County.
Allegan County, Michigan
AQI 43 · 71.2% good
Ashtabula County, Ohio
AQI 43 · 81.2% good
Bell County, Kentucky
AQI 43 · 63.5% good
Boise County, Idaho
AQI 43 · 72.9% good
Brazos County, Texas
AQI 43 · 63.4% good
Broward County, Florida
AQI 43 · 72.4% good
What Allen County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 43 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 Ohio neighbours before drawing a conclusion about the region. All of Ohio
Based on 296 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, Ohio? ▼
Allen County has a median Air Quality Index (AQI) of 43, rated "Good." 65.9% of monitored days (195 out of 296) had good air quality in 2025.
What is the main pollutant in Allen County? ▼
The primary pollutant in Allen County is Fine Particles (PM2.5), which was the main AQI driver on 149 days (50% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
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 129.
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: 2020 with 289 good days. Worst year: 2025 with 195 good days.
What does AQI 43 mean for health? ▼
Allen County's median AQI of 43 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 Ohio? ▼
Allen County has 65.9% good air days. Nearby counties in Ohio: Ashtabula (81.2% good), Athens (80.3% good), Belmont (63.0% good), Butler (33.3% good), Clark (59.4% good), Clermont (72.1% good).
What is the 90th percentile AQI in Allen County? ▼
The 90th percentile AQI for Allen County is 63, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 129 (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.