Which is worse, severe or severe?

Pollution index refers to an index that comprehensively represents the concentration and filtration characteristics of suspended solids and colloidal substances in feed, and represents the degree of blockage of microporous membrane by feed. Air pollution index is a quantitative scaling method to reflect and evaluate air quality. It simplifies the concentrations of several air pollutants that are routinely monitored into a single conceptual index numerical form, and uses grades to represent the degree of air pollution and air quality.

The air quality index (AQI)*** is divided into six levels, ranging from first-class excellent, second-class good, third-class mild pollution, fourth-class moderate pollution to fifth-class severe pollution and sixth-class severe pollution. Among them, the serious pollution is when the AQI reaches 20 1 to 300, and the serious pollution is when the AQI is greater than 300. Serious pollution belongs to the highest level. The index ranges from 20 1 ~ 250 and 250 ~ 300, which are grade ⅳ ⅰ and ⅳ ⅱ respectively. The air quality status belongs to moderate and moderate heavy pollution respectively. Living in such air for a long time may seriously affect everyone's health.

The index is greater than 300, the air quality grade is V, and the air quality status belongs to severe pollution. Living in such air for a long time will seriously affect everyone's health.