The index is based on measurements of the concentrations of five pollutants: PM 10 (particulate matter of 10 micrometers or less), sulfur dioxide, carbon monoxide, nitrogen dioxide, and ozone. Air quality standards have been developed for each of these. For each pollutant, a value of 100 is assigned to the maximum permitted concentration of that pollutant. After determining a value for each of the five pollutants, the highest of the five numbers is reported as the pollutant standards index (PSI) for the day.
- Environmental Protection Administration, R.O.C.(Taiwan)