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The Space Station Internal Thermal Control System (ITCS) fluid formulation is composed of a buffer solution consisting of a mixture of tri-sodium phosphate and sodium borate that produce a pH of approximately 9.5. A silver ion concentration is also specified in the formulation to assist in the control of microorganisms. The specification for the fluid places tight control on the allowed total organic carbon (TOC) concentration to further control possible food sources for microorganisms. Various ground tests conducted on the Laboratory and Airlock modules have demonstrated that the TOC specification is hard to maintain in a test environment. Test data also demonstrate that silver ion depletes as it comes in contact with various metals in the ITCS loop. When the silver is depleted, the microorganism populations can rapidly increase to a range of 105 to 106 colony forming units (CFU) per 100 milliliter.