Abstract: An apparatus and method for vapor sterilization of articles such as medical devices and instruments with lumens. The lumens are connected in a sterilization chamber to a conduit which leads to an exhaust flow restrictor, which exhausts to a vacuum pump. The exhaust flow restrictor has a bypass also which exhausts to the vacuum pump. The majority of the gas from the sterilization chamber flows through the bypass on the exhaust flow restrictor while only a portion of the gas flows through the lumen. Because most of the gas flows through the bypass rather than through the lumens, the sterilization chamber can be pumped down rapidly. The attached lumens are sterilized effectively in spite of the rapid pumpdown rate.