Aerosols are formed by small solid or liquid particles dispersed and suspended in the air, forming a colloidal dispersion system, also known as a gas dispersion system, in which the size of the small solid or liquid particles is 0.001-100μm. clouds, fog, dust in the sky, smoke formed by boilers or unburned objects from various engines in industry or transportation, as well as solid dust formed in mining, quarries and food processing. PM2.5 refers to particulate matter with a diameter of ≤2.5μm in the ambient air, which can be suspended in the air for a longer period of time, and the higher the concentration in the air, the more serious the air pollution. Although PM2.5 is only a small component of the earth’s atmospheric composition, it has an important impact on air quality and visibility. Compared with coarser atmospheric particles, PM2.5 is smaller in diameter, larger in area, more active, more likely to be accompanied by toxic and harmful substances such as heavy metals and microorganisms, and stays in the atmosphere for a longer period of time and is transported over longer distances, thus having a greater impact on human health and the quality of the atmospheric environment. Content source: Dr. You Lai