The vast majority of refrigeration and air-conditioning systems, both residential and commercial, rely on vapor compression systems to remove heat. For decades, ozone-depleting chlorofluorocarbons (CFC) were the refrigerant of choice for such systems. CFCs, however, were banned in the 1990s because of their ozone depletion potential (ODP). This led to an often costly and painful conversion to non-ozone depleting, hydrofluorocarbon (HFCs) refrigerants. For some, especially Europeans, this transition was only a bridge to other refrigerants because of the high global warming potential (GWP) of HFCs. Further research and development has led to increased use of these natural refrigerants, which had once been popular, were displaced, and are now back. These include carbon dioxide (R-744) and hydrocarbons such as isobutane (R-600a) and propane (R-290a). …More