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API and You

Air Pollution Index and Air Quality

How is the API Calculated and Reported? Click to view the photo of monitoring station We report the real-time general and roadside APIs hourly. These indices are calculated by comparing the measured concentrations of the major air pollutants with their respective health related Air Quality Objectives (AQOs) established under the Air Pollution Control Ordinance. These pollutants are nitrogen dioxide, sulphur dioxide, ozone, carbon monoxide and respirable suspended particulates. An index is calculated for each of the five pollutants and the highest index is reported as the API of that hour. The map below shows the locations of air quality monitoring stations.

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