What is the API unit?

API refers to the air pollution index.

English abbreviation for air polarization index.

Air pollution index (API) is a method to reflect and evaluate air quality. It simplifies the concentrations of several air pollutants that are routinely monitored into a single conceptual digital form, and represents air quality status and air pollution degree according to grades. The results are concise, intuitive and easy to use, which is suitable for expressing the short-term air quality status and changing trend in cities. Determination principle of air pollution index: air quality depends on the pollution degree of the most harmful pollutant among all kinds of pollutants. Air pollution index is to determine the classification of pollution index and the corresponding pollutant concentration limit according to the ambient air quality standard and the influence of various pollutants on human health and ecological environment. At present, the classification standard of air index adopted in China is: (1) The pollutant concentration corresponding to 50 points of air pollution index (API) is the first-class standard of national air quality daily average; (2) The pollutant concentration corresponding to API100 is the national secondary standard of daily average air quality; (3) (3) The pollutant concentration corresponding to API 200 is the national daily average level 3 standard of air quality; (The division of API high value segment corresponds to the concentration limit when various pollutants have different effects on human health, and API500 point corresponds to the concentration when various pollutants cause serious harm to human health. According to the characteristics of air pollution in China and the focus of pollution prevention and control work, the pollutants currently included in the air pollution index are tentatively sulfur dioxide, nitrogen oxides and total suspended particulate matter. With the deepening of environmental protection and the improvement of monitoring technology, other pollution projects will be adjusted and increased to reflect the pollution situation more objectively.

Please refer to Baidu Encyclopedia for details:

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