Air quality in Chelmsford, Massachusetts, United States of America today
Mr. Duck’s Air Quality Score
Good air today for Chelmsford, Massachusetts, United States of America
This friendly indicator summarizes the latest city readings. For health guidance, please see: EPA AirNow or WHO.
Air quality today
The air quality in Chelmsford, Massachusetts is rated as Good today. The primary pollutant identified is PM2.5 (fine particles).
Measurements show a PM2.5 concentration of 6.3 µg/m³ based on four valid observations reported through OpenAQ. No PM10 value is available for this assessment. This page is informational; for health guidance, use official sources such as EPA AirNow or WHO.
Latest sensor values
PM categories follow US EPA AQI breakpoints, shown here as an estimate derived from the latest valid measurements (this project does not compute EPA NowCast/24-hour AQI yet).
What the data includes
The Chelmsford air‑quality dataset contains a single monitoring location, identified as ChelmsfordNR, which supplies one row of data for each of the five pollutants tracked: nitrogen monoxide (NO), nitrogen dioxide (NO₂), total nitrogen oxides (NOX), ozone (O₃) and fine particulate matter (PM2.5). All rows are present, giving full coverage of the listed contaminants, but the overall station count is limited to one site.
The most recent measurements for NO, NO₂, NOX and PM2.5 were recorded on 2026‑02‑11 at 00:00 UTC, while the ozone reading dates back to 2024‑05‑23 at 15:00 UTC. This means that four of the five pollutants have data updated within the past seven days, whereas ozone is based on older information. For each pollutant the dataset shows a single value rather than a range: NO is consistently 0.013 ppm, NO₂ 0.017 ppm, NOX 0.030 ppm and O₃ 0.028 ppm; PM2.5 is recorded at 6.3 µg/m³. Because each metric has only one reported figure (minimum, median, maximum and the 10th/90th percentiles are identical), there is no observed variability within this dataset.
Given that the data come from a solitary sensor, they represent conditions at that specific point in Chelmsford rather than city‑wide averages. The freshness of most pollutants is high, but the ozone measurement lags considerably, so current ozone levels cannot be inferred directly from this source. Users should keep in mind that air quality can differ across neighborhoods and times of day, and the limited spatial coverage means the dataset provides a snapshot rather than a comprehensive picture of Chelmsford’s atmospheric conditions.
Learn more about sources and filtering: About the data.
Trusted references: WHO (Air pollution) · US EPA AirNow · European Environment Agency (Air)
Latest sensor values (bars)
PM categories follow US EPA AQI breakpoints, shown here as an estimate derived from the latest valid measurements (this project does not compute EPA NowCast/24-hour AQI yet).
Data notes
The data shown reflects four valid measurements and was updated today (2026‑02‑11T00:00:00+00:00). These values represent a snapshot of ambient conditions across Chelmsford, Massachusetts, but air quality can differ by specific location and time within the city, so individual experiences may vary.
OpenAQ station rows
| Station | Parameter | Value | Unit | Last updated |
|---|---|---|---|---|
| ChelmsfordNR | no | 0.013 | ppm | 2026-02-11 00:00 UTC |
| ChelmsfordNR | no2 | 0.017 | ppm | 2026-02-11 00:00 UTC |
| ChelmsfordNR | nox | 0.03 | ppm | 2026-02-11 00:00 UTC |
| ChelmsfordNR | o3 | 0.028 | ppm | 2024-05-23 15:00 UTC |
| ChelmsfordNR | pm25 | 6.3 | µg/m³ | 2026-02-11 00:00 UTC |