A ventilation assembly for a machine for the preparation of radiopharmaceuticals. The ventilation assembly includes a suction apparatus and release apparatus for generating a circulation of air within a vacuum dispensing chamber, a product filling calibrator accommodated in the dispensing chamber and presenting a cavity accommodating a container to be filled with radiopharmaceutical, and a suction conduit adapted to connect a bottom portion of the accommodating cavity to the suction apparatus for creating a one-way flow in the accommodating cavity. Also, a machine that includes the ventilation assembly.