Air quality · ZIP 03801
Air quality in Portsmouth (NH), NH
ZIP 03801 (New Hampshire) — air quality summary sourced from EPA Air Quality System (AQS), annual county summary. Refreshed on the cadence of the primary regulator with every claim cited to the source record.
Rockingham County (NH), New Hampshire · 2025 annual summary
Median AQI 38 — Good
Air quality is satisfactory, and air pollution poses little or no risk.
- Good days
- 309
- Moderate days
- 54
- Unhealthy for sensitive groups
- 2
- Unhealthy+ days
- 0
- Max AQI
- 150
- 90th percentile AQI
- 54
This is a county-level ANNUAL SUMMARY for 2025, not a live current reading. For today's air quality, check a real-time monitor at airnow.gov. Categories follow EPA's official AQI breakpoints.
What lands here
The 2025 annual EPA Air Quality System summary for this ZIP's county — shown above.
Source & refresh
EPA Air Quality System (AQS), annual county summary. Refreshed annual (epa aqs publication). Stale data is flagged, never silently served. Primary source →
Limitations specific to this source
This is a county-level ANNUAL SUMMARY, not a live current reading and not an address-level measurement — for today's AQI, EPA's real-time AirNow feed is the correct source (not yet federated here). Not every county operates an EPA monitor; absence of data for a ZIP's county means no 2025 EPA reading exists, not that air is good.
New Hampshire context
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.
Read more on air quality
Editorial deep-dives explaining the source data, its limits, and how to read it.
EPA AQI categories explained — what 0–50 Good through 301–500 Hazardous mean
Plain-English guide to the six EPA Air Quality Index categories: 0–50 Good, 51–100 Moderate, 101–150 Unhealthy for Sensitive Groups, 151–200 Unhealthy, 201–300 Very Unhealthy, 301–500 Hazardous — what each level means and who is at risk.
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.
Wildfire Hazard Potential — what the USFS scale means and how to defend your home
Plain-English guide to the USDA Forest Service's Wildfire Hazard Potential 1–5 scale, how to read your community's risk, and concrete home-defense measures.
AirNow + wildfire smoke — when AQI is a real-time tool
How EPA AirNow handles real-time wildfire smoke, what the colors mean during fire season, and where AirNow leaves gaps you should know about.
The other dimensions for ZIP 03801
Air quality is one of twelve public-records dimensions zipradar indexes per address. See the ZIP 03801 index for the other eleven — each with its own regulator, source and link:
All dimensions for Portsmouth (NH), NH →Frequently asked questions
What is the air quality for ZIP 03801?
Rockingham County (NH), New Hampshire (which covers ZIP 03801) had a 2025 median AQI of 38 — Good, per EPA's Air Quality System. Over the year: 309 Good days, 54 Moderate, 2 Unhealthy for Sensitive Groups. This is a county-level ANNUAL SUMMARY for 2025, not a live current reading. For today's air quality, check a real-time monitor at airnow.gov. Categories follow EPA's official AQI breakpoints.
Where does the air quality data come from?
EPA Air Quality System (AQS), annual county summary (primary regulator). zipradar federates air quality on the regulator's published cadence: annual (epa aqs publication). Every claim cites the source record; stale data is flagged, never silently served. The primary source URL: https://aqs.epa.gov/aqsweb/airdata/download_files.html.
What are the limitations of air quality data?
This is a county-level ANNUAL SUMMARY, not a live current reading and not an address-level measurement — for today's AQI, EPA's real-time AirNow feed is the correct source (not yet federated here). Not every county operates an EPA monitor; absence of data for a ZIP's county means no 2025 EPA reading exists, not that air is good.
Is ZIP 03801 (Portsmouth (NH)) data current?
Last verified 2026-09-07. Air quality for ZIP 03801 refreshes annual (epa aqs publication) per EPA Air Quality System (AQS), annual county summary cadence. See the full ZIP dashboard at /zip/03801/ for all 12 dimensions side-by-side.