A method of operating a sterilization system having a vacuum chamber forsterilizinginstruments, the chamber connected to a reservoir of sterilant by a valve in aclosed state, isdisclosed. The method comprises placing the instruments in a non-sterile statein a sterilizationpack, opening the chamber, placing the pack into the chamber, closing thechamber, withdrawinga first volume of air from the chamber, changing a volume of liquid water intovapor, openingthe valve, introducing the sterilant into the chamber, withdrawing thesterilant from the chamber,introducing a second volume of air into the chamber, opening the chamber,removing the packfrom the chamber, and removing the instruments in a sterile-state from thepack. The methodmay also include taking a baseline humidity measurement while the pressurewithin the chamberis a first pressure, lowering the pressure within the chamber to aconditioning pressure,maintaining the conditioning pressure for a dwell time, increasing thepressure within thechamber, acquiring a second humidity measurement from within the chamber, andcomparing thebaseline humidity measurement to the second humidity measurement.
