POLLUTANT STANDARDS INDEX
To let the public better understand the air quality, the monitoring data is transformed to the Pollutant Standards Index (PSI). The monitoring data used to calculate the index is based on the criteria pollutants, I.e., particulate matter (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3). For each pollutant, a subindex is calculated from a segmented linear function that transforms ambient concentrations onto a scale ranging from 0 to 500.


The PSI is calculated as the maximum of sub-index. The index range and descriptor category are as follows:


0 to 50…………………………………….."Good"
51 to 100…………………………………."Moderate"
101 to 199……………………………….."Unhealthy"
200 to 299……………………………….."Very Unhealthy"
300 to above……………………………."Hazardous"