To obtain an appropriate picture of emissions through the aeration lantern of the block based on the location of the experimental area, a flexible shut-off screen was applied together with electrolyzers RA-400. Sampling was carried out along the horizon of the upper edge of the electrolyzer with the fully covered tub and during the exposing by means of the quickdetachable/installed attachments. The study of aerodynamics and the sampling of extended sourcesthe aeration lantern, input ventilation and the area above the depressurized electrolyzerwas carried out under moderate weather conditions (no strong winds) and close to mean standard atmospheric pressure and humidity. According to the results of instrumental studies through the use of formulas for the calculation of aerodynamic parameters, the following characteristics of dust-gas-air flows organized by the gas suction and gas-cleaning systems were calculated: the density of gas medium in operating conditions; the dust-gas-air flow motion speed at the site of measurement; the volume of gas under operating conditions; the volume of gas under normal conditions. With the electrolyzer covered, at the point closest to the gas removal system, the concentration of hydrogen peroxide in the sample was the lowest. Further, with the increasing distance from the gas removal system, the concentration increased slightly, but at both points was below the MAC (maximum allowable concentration). The concentration of hydrogen peroxide (expressed as fluorine) in the gas removal system was defined. In the mode of replacement of anodes, the volume of gas removal increased. The concentration of hydrofluoride was also below the maximum permissible concentration in the operation area. The concentration increases before the anodes replacement point was negligible, and at the third point after the covers removal was quite noticeable. The concentration of hydrogen peroxide (expressed as fluorine) in the gas removal system is defined.