Aerosols

An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or artificial. Examples of natural aerosols are fog, forest exudates and geyser steam. Examples of artificial aerosols are haze, dust, particulate air pollutants and smoke. The liquid or solid particles have diameter mostly smaller than 1 μm or so; larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear-cut. In general conversation, aerosol usually refers to an aerosol spray that delivers a consumer product from a can or similar container. Other technological applications of aerosols include dispersal of pesticides, medical treatment of respiratory illnesses, and combustion technology.Diseases can also spread by means of small droplets in the breath, also called aerosols.

Aerosol science covers generation and removal of aerosols, technological application of aerosols, effects of aerosols on the environment and people, and a wide variety of other topics.

An aerosol is defined as a colloidal system of solid or liquid particles in a gas. An aerosol includes both the particles and the suspending gas, which is usually air.Frederick G. Donnan presumably first used the term aerosol during World War I to describe an aero-solution, clouds of microscopic particles in air. This term developed analogously to the term hydrosol, a colloid system with water as the dispersing medium.Primary aerosols contain particles introduced directly into the gas; secondary aerosols form through gas-to-particle conversion.

Various types of aerosol, classified according to physical form and how they were generated, include dust, fume, mist, smoke and fog.

...
Wikipedia