The invention relates to a method and device for optimizing the cleaning properties of fog by measuring electrical signals from the surface photo-charge effect, which depends on the amount of impurity absorbed by the fog. For this purpose, modulated radiation induces an electrical signal that changes at different concentrations of the impurity. The method for optimizing the cleaning properties of fog is carried out by means of a laser-induced surface photo-charge effect. Signals from mists with impurities of different numbers and diameters of droplets are measured. The strongest signal deviation is recorded, corresponding to the largest amount of impurity carried by the mist droplets. In this way, the parameters of the mist at which the absorption of the impurity is best are determined. The device for optimizing the cleaning properties of fog consists of a sensor that generates a signal sensitive to the composition of the fog with which it is in contact. The sensor is irradiated with modulated laser radiation, and the generated signal is observed on a nanovoltmeter. The device and method allow the concentrations of impurities in the composition of fogs and aerosols to be determined, which can be used for environmental control, elimination of the consequences of pollution, in ecology, occupational safety, and others.