Contractors hoping for the final word on the newest refrigerants may not have to wait much longer. Research continues by manufacturers and universities on the newest gases, and most of the studies are focusing on low-global warming potential (GWP) hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs). But the good news for some is that what is currently being worked on could well represent the last generation of refrigerants.