Fan local ventilation shafts, comprising two basic modules of the 1st and the 2nd fan stages coupled between a connecting body insert so that each module comprises a housing, a motor, an impeller mounted directly on the motor shaft, characterized in that the impellers 1st and 2nd stages performed according to the scheme counter rotating, twin-welded with the non-rotatable leaf blades S-shaped impeller with variable radius geometry, calculated by the "dis indiscrete vortex "as employed together without the flow straightener of the lower acoustic power conditions (noise) of the fan, the greatest efficiency, pressure and performance.
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