ABSTRACT
In this chapter, the term aerosol was defined. The basic sources of aerosol particles and their classification were discussed. The most important characteristics describing the population of aerosol particles were defined: size distribution, shape and concentration. The basic definitions allowing us to determine different diameters of particles and their numerical, mass and volumetric concentration per unit of air were given. Functions describing particle size distribution and the main values of these distributions were given. The concept of fractal-like aggregate was defined, and its most important features influencing the fluid flow behavior and its harmful nature for human health were discussed. The definitions of bioaerosols and their basic characteristics were given.
