FIELD: construction.SUBSTANCE: method consists in supplying clean air to the space of an open vertical borehole - a well or a slurry pit under pressure, with the possibility of increasing its speed at the bottom of the open vertical bore - a well or a slurry pit, and removing polluted air by a draft source, creating vacuum in the well up to 0.4 kg/cmwith the continuous determination of the type of a gas and its concentration. Then the process is repeated, until the permitted concentration of polluted air is reached as per all parameters. Further, alternately, clean air is injected into the space of an open vertical borehole - a well or a slurry pit within 5 min under a pressure of up to 2.8 kg/cmand polluted air is removed for 5 min. Thereinafter, the air supply to the pressure duct is reduced to 50% of the initial air supply, and the process is repeated. The device comprises a vertical borehole, an air blower, a pressure pipeline and a discharge pipeline, connected to the draft source. Each of the pipelines in the bottom part has openings at an equal distance from one another by the pipeline height with the uniform reduction of the opening diameters from the Laval nozzle. The opening diameters of the bottom row are larger than the opening diameters of the top row by 2 times, with a pitch by height of 0.1 of the pipeline diameter, and the total area equal to 25% of the pipeline cross-section area. The openings are located in the horizontal plane of the pipeline cross-section symmetrically to one another and with the displacement of the horizontal rows of the openings relative to the previous row. A gas content sensor is installed on the discharge pipeline. As an air blower, a centrifugal compressor or a turbocharger is used, at the inlet of which a damper is installed. On each of the pressure pipeline and the discharge pipeline, in their bottom part, 3-4 rows of arched pipelines with a length of no more than 0.5 of the diameter of the vertical borehole, and a straight pipeline between them, in length not exceeding 0.4 times the vertical borehole radius, located in one horizontal plane with the arched pipelines. The diameters of these pipelines are equal to one another, and openings of the same diameter are made on the arched and straight pipelines along their length. The diameters of the openings in these pipelines are equal to the diameters of the openings of the pressure pipeline or the discharge pipeline at the location level of the arched and the straight pipelines. The solenoid valve of the pressure pipeline has a flow cross-section 2 times smaller than the flow cross-section of the solenoid valve of blown air discharge to the atmosphere.EFFECT: increasing the efficiency and speed of cleaning the well from harmful gases while simplifying the device design.2 cl, 2 dwg