Median AQI
41
Good
Massachusetts · County air quality · 2025
Hampden County, Massachusetts
Median AQI 41 (Good). 72.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 41
- Median AQI
- 72.2%
- Good-air days
- 0
- Unhealthy days
- 36%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Hampden County's air is good on balance, more polluted than the median US county, a median AQI of 41 with 72.2% of 248 monitored days in the Good band, driven mainly by Ozone.
- 41
- median AQI · Good
- 72.2%
- days rated Good
- Ozone
- main pollutant
- 36%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 124.
Data updated July 2026
- Good · 179 d · 72.2%
- Moderate · 64 d · 25.8%
- USG · 5 d · 2.0%
How did Hampden County's air break down in 2025?
Across 248 monitored days, 179 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 124 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 248 days monitored. Median AQI: 41 (Good).
Insights: Hampden County, Massachusetts. EPA monitors recorded a median Air Quality Index of 41 across 248 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 179 (72%) fell in the Good band (AQI 0–50), 64 (26%) registered Moderate readings, and 5 (2%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 64, while the worst single-day peak hit 124 (USG). Residents averaged about 21.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (155 days), PM2.5 (86 days), NO2 (7 days). Across the 2020–2025 trend window, good days shifted by -70 and the median AQI moved -3 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 124, usg but never Unhealthy. Nearby counties show comparable readings: Barnstable (92.5% good, AQI 38); Berkshire (71.6% good, AQI 41); Bristol (77.8% good, AQI 41); Dukes (95.2% good, AQI 37); Essex (77.0% good, AQI 42); Franklin (72.8% good, AQI 40).
Air Quality Summary
Good Days
72.2%
179 of 248 monitored days
-2.8pp vs 75% target
Max AQI Recorded
124
USG
Health Grade
Moderate
90th-pct AQI 64
Hampden County, Good days share 72.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Hampden 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 248 monitored days across EPA AQI categories.
Good
179
72%
Moderate
64
26%
USG
5
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 Hampden County.
- Ozone · 155 days · 62.5%
- PM2.5 · 86 days · 34.7%
- NO₂ · 7 days · 2.8%
Health Impact Assessment
Moderate
Hampden County's air quality is rated Moderate based on 72.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 72.2% of monitored days in 2025, with a median AQI of 41. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 155 of 248 monitored days.
5-Year Air Quality Trend
Air quality is improving in Hampden County. Best year: 2024 (290 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 249 | 117 | 0 | 0 | 44 | 99 |
| 2021 | 215 | 148 | 2 | 0 | 46 | 116 |
| 2022 | 262 | 102 | 1 | 0 | 42 | 115 |
| 2023 | 220 | 139 | 4 | 2 | 46 | 153 |
| 2024 | 290 | 74 | 2 | 0 | 37 | 119 |
| 2025 | 179 | 64 | 5 | 0 | 41 | 124 |
How does Hampden County compare?
How Hampden County compares
Good-day share worse than US avg
Hampden County 72.2%
Barnstable County, Massachusetts 92.5%
US average 76.5%
Median AQI worse than US avg
Hampden County 41
Barnstable County, Massachusetts 38
US average 38
Unhealthy days / yr about average
Hampden County 0
Barnstable County, Massachusetts 0
US average 0
Other Counties in Massachusetts
Air quality comparison for nearby counties in Massachusetts.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Hampden County.
Albemarle County, Virginia
AQI 41 · 77.9% good
Anderson County, South Carolina
AQI 41 · 90.0% good
Berkshire County, Massachusetts
AQI 41 · 71.6% good
Berrien County, Michigan
AQI 41 · 80.9% good
Blair County, Pennsylvania
AQI 41 · 71.9% good
Bonner County, Idaho
AQI 41 · 71.3% good
What Hampden 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 41 means for exposure. Health guidance
- See how Hampden County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Hampden County with its Massachusetts neighbours before drawing a conclusion about the region. All of Massachusetts
Based on 248 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 Hampden County, Massachusetts? ▼
Hampden County has a median Air Quality Index (AQI) of 41, rated "Good." 72.2% of monitored days (179 out of 248) had good air quality in 2025.
What is the main pollutant in Hampden County? ▼
The primary pollutant in Hampden County is Ozone (O3), which was the main AQI driver on 155 days (63% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Hampden County have? ▼
In 2025, Hampden County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 124.
Is the air quality in Hampden County getting better or worse? ▼
Air quality in Hampden County is improving based on 5-year trends (2020-2025). Best year: 2024 with 290 good days. Worst year: 2025 with 179 good days.
What does AQI 41 mean for health? ▼
Hampden County's median AQI of 41 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 Hampden County compare to other counties in Massachusetts? ▼
Hampden County has 72.2% good air days. Nearby counties in Massachusetts: Barnstable (92.5% good), Berkshire (71.6% good), Bristol (77.8% good), Dukes (95.2% good), Essex (77.0% good), Franklin (72.8% good).
What is the 90th percentile AQI in Hampden County? ▼
The 90th percentile AQI for Hampden County is 64, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 124 (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.