Air quality in Sejong, South Korea today

Mr. Duck’s Air Quality Score

Unhealthy for sensitive groups for Sejong, South Korea

⚠️ This website is currently under active development. Some data may be incomplete or temporarily inaccurate. For health-critical decisions, please verify information through official government or environmental sources.

Categories follow US EPA AQI breakpoints for PM (estimate from latest valid measurements; this project does not compute EPA NowCast/24-hour AQI yet).

This friendly indicator summarizes the latest city readings. For health guidance, please see: EPA AirNow or WHO.

Air quality today

The overall air quality today is classified as USG. The primary pollutant measured is PM2.5 (fine particles). The reported PM2.5 concentration is 47.0 µg/m³ and the PM10 concentration is 64.0 µg/m³. These figures are derived from 34 valid measurements taken across monitoring locations in Sejong. The average of the valid readings forms the basis of the presented concentrations. Data is shown via OpenAQ.

OpenAQ aggregates the measurements from local monitoring stations and makes them publicly available. The 34 valid readings provide a snapshot of particulate levels for the city at the time of collection. The snapshot reflects the concentration of fine particles (PM2.5) and inhalable particles (PM10) measured during the sampling period. 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 Sejong air‑quality record pulls data from six monitoring stations, giving a total of thirty‑six recent rows. All six pollutants—carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), particulate matter 10 µm (PM10), particulate matter 2.5 µm (PM2.5) and sulfur dioxide (SO2)—are represented, and each measurement was last refreshed on 2026‑02‑10 18:00 UTC, well within the thirty‑day freshness window.

Across the dataset CO values span from a low of 0.25 ppm to an extreme high of 9 999 ppm, with a median of 0.595 ppm; the tenth percentile sits at 0.29 ppm and the ninetieth at 4 999.84 ppm, indicating a very wide spread and the presence of outlier readings. By contrast, NO2 shows a tighter band, ranging from 0.0089 ppm to 0.0215 ppm, a median of 0.0151 ppm, and a ninety‑percentile just under 0.021 ppm. Ozone follows a similar pattern, moving between 0.0064 ppm and 0.0359 ppm, with a median of 0.02195 ppm and a ninety‑percentile of 0.03295 ppm. Particulate matter displays moderate variability: PM10 ranges from 34 µg/m³ to 64 µg/m³, median 54 µg/m³, with most values (10‑90 percentile) between 35 and 60 µg/m³. PM2.5 spans 16 µg/m³ to 49 µg/m³, median 38 µg/m³, and a tighter central band of 21.5‑48 µg/m³. SO2 also has an extreme maximum of 9 999 ppm, but its typical range is 0.0021‑0.0033 ppm, median 0.00305 ppm, and a ninety‑percentile near 4 999.5 ppm, again suggesting occasional outlier entries.

Overall, the snapshot provides a recent, city‑wide view from multiple sites, yet the presence of very high maximum values for CO and SO2 signals that some rows may contain placeholder or erroneous data. While most pollutants show compact, consistent distributions, the data set’s breadth across six stations means conditions can still differ by neighborhood and moment, and the current snapshot captures only a single point in time.

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 dataset for Sejong includes 34 valid measurements and is Updated within 30 days. The most recent data were recorded on 2026-02-10 at 18:00 UTC. This snapshot reflects conditions at the time of sampling, but air quality can vary by location and time within the city. Users should consider this variability when interpreting the values.

OpenAQ station rows