A chamber (10) is supplied with a pressurized cleaning agent of carbon dioxide and cosolvents from a first source (12) and an antimicrobial fluid, such as ethylene oxide or hydrogen peroxide from a second source (16). Chamber conditions are maintained in the sub-critical range for the carbon dioxide. The cleaning agent and antimicrobial fluid are recirculated through a separator (32) and a condenser (38) to filter contaminants from the mixture before returning the carbon dioxide, and optionally the antimicrobial fluid and other additives, to the chamber. Medical instruments or other articles within the chamber are cleaned by the cleaning agent and sterilized by the antimicrobial fluid in a single cycle, rendering them ready for reuse in a short period of time. The instruments may be cleaned and stored in hermetically sealable containers (82). The cleaning agent is rapidly evaporated from surfaces of the articles at the end of the cycle by reducing the pressure in the chamber. Optionally, a vacuum pump (60) assists in removing the antimicrobial fluid from the chamber.