A chemical vapor sterilization process is enhanced by concentrating a germicide via exploitation of the difference between the vapor pressures of the germicide and its solvent. A diffusion restriction can be placed into the diffusion path to assist this process and the path then opened to provide rapid diffusion of the thus concentrated germicide. The path through the diffusion restriction can be closed to allow the pressure in a sterilization chamber to be lowered prior to receiving the concentrated germicide.
