Updating the limited options for low-global-warming-potential refrigerants

In 2017, McLinden et al. ( McLinden et al., 2017 ) Nat. Comm. 2017, 8 , 14476 carried out a comprehensive survey of possible replacements for the hydrofluorocarbon (HFC) refrigerants, which are currently being phased down under an international treaty. They showed that only a few pure fluids possess the combination of chemical, environmental, thermodynamic, and safety properties necessary for a refrigerant and that these fluids are at least slightly flammable. In this review paper, we revisit and update that analysis. While a very limited number of new fluids have been added to the list, primarily due to new data becoming available, no new class of chemicals has emerged. However, new safety data and protocols now allow the use of flammable refrigerants in some applications. On the other hand, new regulations, which will likely vary by region, may further restrict the choice of refrigerants.