A multi-stage steam ejector or optional evacuation system is used to reduce the chamber to 6 to 8 TORR. This is important since steam entering a mass of tobacco will push air ahead of it to form a bubble. Should such a bubble remain, it would prevent moistening of the tobacco in contact with it and unmoistened cold centers could result. Steaming continues until moistening is complete, air bubbles are purged; and the desired temperature such as 71°C is obtained.

In some other types of conditioning units, this introduction of steam completes the cycle. The Vacudyne Hi-Vac system conditioning process utilizes from two to five steps of alternate evacuation and steaming which not only achieves uniform moistening, but upon re-evacuation removes certain non-condensable vapors from the tobacco. Not only does it remove undesirable elements by achieving an absolute pressure of approximately 50 TORR, but also fluffs the tobacco as the vapors in the tobacco are expanded. This fluffing also prepares the leaf for final introduction of moisture that follows. An additional benefit of the Hi-Vac process is the elimination of any insect infestation in the tobacco.