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Introduction
Aerosols are present in virtually every aspect of life.
From small and mid-range scale industrial processes, such as those producing glass particles,
large scale processes, such as environmental pollution, dust storms and hurricanes, to even
such large-scale processes as the formation of stars,
interactions involving aerosols form an important part of the world around us.
Definition: An aerosol is a suspension of solid or liquid particles in a gas. Dust, smoke, mists, fog, haze, and smog are various forms of common aerosols. Aerosol particles are found in different shapes (isometrics, platelets, and fibers) and different sizes. For irregular shaped particles, different equivalent diameters are defined. Examples of equivalent diameters include
The range of diameters of common aerosol particles is between 0.01 and 100 µm. The lower limit of 10 nm roughly corresponds to the transition from molecule to particle. Particles larger than 100 µm normally do not remain suspended in air for a sufficient amount of time. Noting that the mean free path for air is about 0.07 µm and visible light has a wavelength band of 0.4 – 0.7 µm, the mechanical and optical behaviors of particles are significantly affected by their size. |
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