What is characterized as a refrigerant blend?

A refrigerant blend is defined as a mixture of two or more refrigerants combined in specific proportions. These blends are often designed to optimize performance, efficiency, and environmental impact compared to single-component refrigerants. The individual refrigerants in a blend can offer complementary properties, such as improved energy efficiency, lower flammability, or reduced ozone depletion potential.

In the context of refrigerants, a blend may be categorized as either an azeotropic blend, which behaves as a single substance in terms of pressure and temperature during phase changes, or a non-azeotropic blend, which does not maintain the same vapor-liquid balance, leading to a change in composition upon evaporation or condensation. This distinction is important for proper handling, charging, and servicing of refrigeration systems.

The other choices refer to different concepts: altering a refrigerant does not make it a blend; a single type of refrigerant indicates no blending at all; and an unapproved refrigerant does not fit the definition of a blend regardless of how many different refrigerants it comprises. Thus, the characterization of a refrigerant blend is accurately captured by identifying it as a mixture of two or more refrigerants.