Air quality · New Hampshire
Air quality in New Hampshire
Across the 3 New Hampshire ZIPs with EPA county air-quality data, the median day is Good in all 3 (median AQI 37–38). No day in those counties reached Unhealthy in 2025. This is a 2025 county annual summary, not a live reading.
Last verified 2026-09-24 · methodology
Air quality by ZIP code in New Hampshire
EPA's 2025 annual summary for each ZIP's county. Median AQI is the typical day; lower is cleaner.
| ZIP | Median AQI | Good days | Unhealthy or worse |
|---|---|---|---|
| 03301ConcordMerrimack County | 37 Good | 205 of 212 | 0 |
| 03101Manchester (NH)Hillsborough County | 38 Good | 310 of 365 | 0 |
| 03801Portsmouth (NH)Rockingham County | 38 Good | 309 of 365 | 0 |
County-level figures from EPA Air Quality System (AQS), annual county summary, joined to each ZIP by county. None of them is a measurement at a specific address.
What lands here
Pages show the 2025 median AQI category (Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, Hazardous) for the ZIP's county, plus the year's max/90th-percentile AQI and day-count breakdown by category.
Source & refresh
EPA Air Quality System (AQS), annual county summary. Refreshed annual (epa aqs publication). Primary source →
New Hampshire top concern
Radon, lead in older housing
New Hampshire is uniformly Zone 1 radon. Older Manchester + Nashua + Portsmouth housing stock carries lead-service-line risk. Coastal flood zones limited to small NH coastline.
See New Hampshire state page for the full state-level rollup across all 12 dimensions.
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AQI explained — what 50, 100, 150 actually mean for your lungs
Plain-English guide to the EPA Air Quality Index (AQI) and the 6 categories from Good to Hazardous. When to take precautions and which pollutants matter.
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AirNow + wildfire smoke — when AQI is a real-time tool
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