What does it mean that the air quality in the weather forecast exceeds the standard?

Off-chart: the original meaning refers to the explosion of the instrument, which usually means that the pointer of the instrument exceeds the limit shown on the table. In recent days, the word "off the charts" has become a hot word. "Exceeding the standard" is the nickname of netizens for the air quality index (AQI) exceeding the standard. In air testing, the highest value set by the air quality index is 500, and the AQI exceeding 500 is "off the chart".

Including:

1. Air pollution index (API) is a method to reflect and evaluate air quality. It simplifies the concentrations of several air pollutants routinely monitored into a single conceptual numerical form, and uses grades to represent air quality status and air pollution degree. 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. According to the characteristics of air pollution in China and the key points of pollution prevention and control, the items currently included in the air pollution index are tentatively set as: sulfur dioxide, nitrogen oxides and total suspended particulate matter. Tmall USA Puwechat

2. Main pollutants.

3. Air quality level: China's air quality is evaluated by air pollution index. Air pollution index is to determine the classification of pollution index and the corresponding pollutant concentration value according to the ambient air quality standard and the influence of various pollutants on human health and ecological environment. The air pollution index (API) currently used in China is divided into five grades, and the API value is less than or equal to 50, which means that the air quality is excellent, which is equivalent to the first-class national air quality standard and meets the air quality requirements of areas requiring special protection such as nature reserves and scenic spots. The API value is greater than 50 and less than or equal to 100, indicating that the air quality is good, which is equivalent to reaching the national secondary quality standard; The API value is greater than 100 and less than or equal to 200, indicating that the air quality is slightly polluted, which is equivalent to the national third-class air quality standard; An API value greater than 200 indicates that the air quality is poor, which is called moderate pollution and is the national air quality level 4 standard. API greater than 300 indicates that the air quality is extremely poor and has been seriously polluted.

4. Air quality status.