The processes of coagulation and dispersion of droplets can occur in polydisperse liquid aerosols (fogs) as a result of external aerodynamic action. This affects the total surface of polydisperse aerosol droplets, which determines the duration of aerosol sedimentation, evaporation intensity and distribution. This is of great practical importance for assessing the behavior of aerosol clouds formed as a result of an explosion, mechanical crushing when a liquid falls from a high altitude, or when it is blown by the gas flow. These situations are characteristic of man-made disasters or chemical means of warfare. It has been established that the nature of the processes is determined by the speed of gas in relation to droplets of polydisperse aerosol. There is a critical gas speed that determines the direction of the processes of changing the surface of the polydisperse aerosol. At a speed less than the critical one, the coagulation processes occur and the surface of the aerosol decreases. At speeds exceeding the critical speed, in parallel with coagulation, the process of droplets сrushing begins, which leads to an increase in the aerosol surface. The mathematical dependence of the relative aerosol surface on the ratio of the gas velocity to the critical velocity has been obtained. This dependence has the character of a quadratic function. The magnitude of the critical velocity depends on the critical value of the Weber criterion (We). It is recommended to take the critical value of the Weber criterion Wecr = 1.3 for the aerosols of mechanical origin