The paper deals with the issue of determination the concentration of solid aerosols, provides various methods and focuses in detail to determine the concentration of solid aerosols using a device that works on the principle of light scattering. The paper includes an explanation of this principle and points out its advantages and possibilities of using in practice. The paper also presents the results of experimental measurements in two classrooms with different boards. The result of the experiment is to determine the concentration of solid aerosols, results of measurements and highlight the differences in the concentration of solid aerosols in different classrooms.