A method of sterilizing an article includes receiving the article in a sterilization chamber. The method also includes applying a vacuum to a first pressure less than 100 torr. The method also includes introducing a sterilant into the sterilization chamber. The method also includes maintaining the first pressure in the sterilization chamber for a first period of time. The method also includes venting the sterilization chamber to a second pressure less than 100 torr. The method also includes maintaining the second pressure. The method also includes venting the sterilization chamber to a third pressure. The method also includes maintaining the third pressure. The method also includes venting the sterilization chamber to atmospheric pressure. The method further includes between venting and maintaining steps applying a vacuum to a fourth pressure less than 100 torr, introducing additional sterilant, and maintaining the fourth pressure.
