Abstract: A method of disinfecting a fluid circuit of a thermal control for delivering temperature controlled fluid to at least one patient therapy device comprises the steps of providing an aqueous mixture comprising a disinfectant and circulating the aqueous mixture in the thermal control unit to disinfect the fluid circuit. The disinfectant comprises free-chlorine, a phenol, hydrogen peroxide (H2O2), or combinations thereof. If the disinfectant comprises free-chlorine, the free-chlorine is provided by a chlorinated isocyanurate (e.g. sodium dichloroisocyanurate; NaDCC). In addition, the free-chlorine is present in the aqueous mixture in an amount of at least about 100 parts per million (ppm). If the disinfectant comprises the phenol, the phenol is natural (e.g. thymol). In addition, the phenol is present in the aqueous mixture in an amount of at least about 10,000 ppm. If utilized, H2O2 is present in the aqueous mixture in an amount of at least about 5,000 ppm.