Discussing new developments for ammonia sounds like a paradox, as ammonia is one of the oldest industrial refrigerants. As emphasized by J.W. Pillis, it never stopped being a leading refrigerant for large systems used in food industry and for other industrial applications. After losing market share to R-22 in recent decades, it is making a strong comeback due to the pressure to phase out R-22. Some major food industry companies have a clear strategy of using only ammonia for their new investments, and to retrofit their existing plants worldwide.