Aerosol is a colloidal dispersion formed by small solid or liquid particles dispersed and suspended in a gas medium, also known as gas dispersion system. Its dispersed phase is solid or liquid particles with the size of 10-3 cm ~ 10-7 cm, and the dispersion medium is gas. Clouds, fog, dust in the sky, smoke from unburned fuel in boilers and various engines used in industry and transportation, solid dust formed in mining, quarry grinding and grain processing, artificial masking smoke and toxic smoke are all concrete examples of aerosols.
The chemical composition of aerosol is very complex, containing various trace metals, inorganic oxides, sulfates, nitrates and oxygen-containing organic compounds.