Air Quality in Yilan County

The Air Quality Index (AQI) is an indicator defined by Taiwan's Ministry of Environment (MOENV). It integrates multiple air pollutants including PM2.5, PM10, Ozone (O3), Carbon Monoxide (CO), Sulfur Dioxide (SO2), and Nitrogen Dioxide (NO2) into a single 0-500 scale to communicate air cleanliness and associated health effects.

PM2.5 refers to fine particulate matter with a diameter of 2.5 micrometers or less. Due to their minute size, they can penetrate deep into human lungs and enter the bloodstream, aggravating asthma, bronchitis, and increasing risks of cardiovascular disease and long-term lung conditions.

The 8-hour ozone reading is the average ozone concentration measured over the most recent continuous eight-hour period. It reflects sustained exposure rather than a single hourly fluctuation and is an important basis for evaluating ozone-related AQI and health risks. It may therefore differ from the current one-hour O3 reading.

When AQI exceeds 100 (Orange level: Unhealthy for Sensitive Groups), children, the elderly, and individuals with respiratory or cardiovascular conditions should reduce prolonged outdoor physical exertion. If AQI exceeds 150 (Red level: Unhealthy), the general public is also advised to wear masks and minimize strenuous outdoor activities.

OpenViz synchronizes hourly with the official open data feed published by the Ministry of Environment. The platform automatically refreshes monitoring data every hour.

Air quality is influenced by localized emission sources (such as heavy traffic corridors, industrial parks, or construction sites), topographical microclimates (basin effects), and prevailing wind directions. Stations located along major roads or inland basins often exhibit higher pollutant concentrations than coastal or hillside stations.