An arrangement is provided to prevent emissions of hydrogen peroxide from a packaging machine forming sealed packaging containers from a packaging material web. The packaging machine has a sterilization portion comprising an inlet chamber, a peroxide bath and an aseptic chamber. The aseptic chamber is held at an overpressure while the inlet chamber is held at an underpressure during normal operation of the packaging machine. The peroxide bath functions as a seal between the inlet chamber and the aseptic chamber. A safety chamber placed in front of the inlet chamber is held at an underpressure to avoid peroxide emissions to the environment. The packaging material web will pass the safety chamber before going into the inlet chamber.