Patent ID: 8366995

Claim:
A method for sterilizing a load in a chamber, said chamber coupled to a vapor sensor, a pressure sensor, a source of gas, an evacuation pump, and a sterilant source, the method comprising: (a) placing the load in the chamber; (b) operating the evacuation pump to decrease the pressure within the chamber; (c) admitting sterilant into the chamber for a predetermined period of time so that the concentration of sterilant in the chamber is at least substantially at a first predetermined target level; (d) allowing the sterilant within the chamber to diffuse for a first diffusion period; (e) monitoring the concentration of sterilant in the chamber to determine the quantity of sterilant that must be added to the chamber, and to calculate the period of time required to admit that quantity of sterilant into the chamber to raise the concentration to substantially a second predetermined target level; (f) admitting additional sterilant into the chamber for said calculated period of time; (g) allowing the sterilant within the chamber to diffuse for a second diffusion period; and (h) after said second diffusion period, admitting a sufficient quantity of gas to increase the pressure within the chamber such that said gas and said sterilant diffuse.