Air Pollution Index

The Air Pollution Index (API) is a simple and generalized way to describe the air quality, which is used in Malaysia. It is calculated from several sets of air pollution data. It was formerly used in mainland China and Hong Kong. In mainland China the API was replaced by an updated Air Quality Index in early 2012 and on 30 December 2013 Hong Kong moved to a health based index.

The air quality in Malaysia is reported as the API (Air Pollutant Index) or in Malay as IPU (Indeks Pencemaran Udara). Four of the index's pollutant components (i.e., carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide) are reported in ppmv but PM₁₀particulate matter is reported in μg/m³.

This scale below shows the Health classifications used by the Malaysian government.

API

Air Pollution Level

If the API exceeds 500, a state of emergency is declared in the reporting area. Usually, this means that non-essential government services are suspended, and all ports in the affected area are closed. There may also be a prohibition on private sector commercial and industrial activities in the reporting area excluding the food sector.

The highest API value ever recorded was 1,986 in Palangkaraya on 22 September 2015 during the 2015 Southeast Asian haze.

China's State Environment Protection Agency (SEPA) is responsible for measuring the level of air pollution in China. As of 28 August 2008, SEPA monitored daily pollution level in 86 of its major cities. The AQI level was based on the level of 5 atmospheric pollutants, namely sulfur dioxide (SO₂), nitrogen dioxide (NO₂), suspended particulates (PM₁₀), carbon monoxide (CO), and ozone (O₃) measured at the monitoring stations throughout each city.

AQI Mechanics
An individual score is assigned to the level of each pollutant and the final AQI is the highest of those 5 scores. The pollutants can be measured quite differently. SO₂, NO₂ and PM₁₀ concentration are measured as average per day. CO and O₃ are more harmful and are measured as average per hour. The final AQI value is calculated per day.

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