Pass box, also called pass-through box, transfer hatch, or pass-thru hatch, is a cleanroom equipment mounted between two rooms or areas, through which materials, small or big, can be transferred between the two rooms or areas, thus saving the trouble of entering and leaving cleanroom, minimizing the air turbulence of opening and closing the doors, more importantly, lowering down or prevent from the risk of cross-contamination between the two rooms or areas.