AZEOTROPE: a mixture of two or more refrigerants in which the liquid and vapor have same composition at equilibrium. In addition, the resulting pressure of the mixture is either higher or lower than the pressure of any of the components. Azeotropes behave like pure component refrigerants because there is no change in boiling temperature or shift in composition during phase change, equipment operation, or leakage.

R-500: Designed to be a higher capacity R-12 type refrigerant, R-500 found some use in air conditioning and dehumidifier equipment and in positive pressure centrifugal chillers.
An EPA certification card is required to purchase CFC and HCFC refrigerants.