Instrument cassette for handling instruments

An instrument cassette for handing instruments, the instrument cassette comprising:

• support structures for mechanically supporting the instruments, and
• at least one shielding structure for containing operational portions of the instruments and for reducing a risk of unintentional touching the operational portions of the instruments,
• wherein at least one wall of the shielding structure comprises channels for allowing liquid and gaseous substances to flow through the wall, characterized in that the channels are shaped so that a straight and unbending round rod having a diameter more than 1.5 mm is incapable of penetrating the wall via the channels when the straight and unbending round rod is perpendicular to a geometric plane parallel with the wall so as to prevent the operational portions of the instruments from protruding through the wall via the channels, and a bendable round rod having a diameter more than 1.5 mm is capable of penetrating the wall via the channels so as to provide cross-sectional flow area for the liquid and gaseous substances.