Dry Sterilisation Process - Procedure

Procedure

At first the bottles are placed into a sterilisation chamber. This chamber is designed to be a vacuum chamber and is evacuated by vacuum pumps down to the low vacuum range. A certain amount of aqueous solution of hydrogen peroxide is now delivered to an evaporator and abruptly evaporated. Driven only by the pressure difference between the hydrogen peroxide vapor inside the evaporator and the evacuated sterilisation chamber, the vapor flows through an appropriate piping into the sterilisation chamber. The vapor is strongly expanding when it enters the chamber, undercooled thereby and instantaneously condensing. The forming condensate layer is covering all surfaces inside the sterilisation chamber, all inner and outer bottle surfaces and all surfaces of the chamber itself.

The heat of vaporization, released by the phase change from gaseous to liquid, heats the forming condensate layer in such a way, that most of the hydrogen peroxide molecules are thermally dissociated thereby. The resulting free radicals, particularly the oxygen atoms, are immediately killing all the germs adhered to the surfaces already during the condensation. In contrast to other sterilisation processes the killing of the germs occurs instantaneously without any need for residence time.

The condensate layer is removed from the sterilisation chamber and all bottle surfaces immediately after the condensation. This is performed only by means of appropriate vacuum pumps which reduce the pressure inside the sterilisation chamber below 1 Torr. The condensate is rapidly re-evaporating when the decreasing chamber pressure reaches the condensates vapor pressure and the forming vapor is removed from the chamber by the vacuum pumps. This re-evaporation effects a total drying of the bottles and the surfaces inside of the sterilisation chamber and completely removes all hydrogen peroxide.

Prior to deloading of the bottles from the sterilisation chamber, the chamber is vented to ambient pressure with sterile air to avoid recontamination of the sterile bottles.