A load lock in which the pumping speed is controlled so as to minimize the possibility of condensation is disclosed. The load lock is in communication with a vacuum pump and a valve. A controller is used to control the valve such that the supersaturation ratio within the load lock does not exceed a predetermined threshold, which is less than or equal to the critical value at which vapor condenses. In certain embodiments, a computer model is used to generate a profile, which may be a pumping speed profile or a pressure profile, and the valve is controlled according to the profile. In another embodiment, the load lock comprises a temperature sensor and a pressure sensor. The controller may calculate the supersaturation ratio based on these parameters and control the valve accordingly.