Abstract: An extractor to be used in the natural ventilation of industrial buildings, for increasing the air flow during the summer season. The extractor, installed on the outside of openings provided in the roof or walls of the buildings to be ventilated, essentially comprises at least one free flow section associated to at least one controlled flow section, such as a "Mueller" static extractor, and provides means for subdividing said free flow section, consisting of rotary blades, and adjustment means interposing between the free flow section and the openings.