Air Pollutant Index (API) Reading | Department of Environment

Air Pollutant Index (API)

The air quality in Malaysia is described in terms of Air Pollutant Index (API). The API is an indicator of air quality and was developed based on scientific assessment to indicate in an easily understood manner, the presence of pollutants and its impact on health. The API system of Malaysia closely follows the Pollutant Standard Index (PSI) developed by the United States Environmental Protection Agency (US-EPA).

The air pollutant index scale and terms used in describing the air quality levels are as follows :

API scale	Air quality
0 – 50	Good
51 – 100	Moderate
101 – 200	Unhealthy
201 – 300	Very unhealthy
301 and above	Hazardous

The CAQM stations measure the concentration of 5 major pollutants in the ambient air, namely, suspended particulate matters (PM10), sulphur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3). These concentrations are measured continuously on hourly basis. The hourly value is then averaged over 24-hour running period for PM10 and SO2, 8-hour period for CO, whilst O3 and NOx are read hourly. An hourly index is calculated for each pollutant. The highest index value recorded is then taken as the API for the hour.

Air Pollutant Index Daily Reading