This AIR is arranged in the following two sections: 2E - thermodynamic characteristics of working fluids, which contains thermodynamic diagrams for a number of working fluids currently in use and supplied by various industrial firms; and 2F - properties of heat transfer fluids, which contains data, primarily in graphical form, on fluids that are frequently used in fluid heat transfer loops. Other properties of the environment, gases, liquids, and solids, can be found, as follows, in AIR 1168/9: 2A-Properties of the natural environment; 2B-Properties of gases; 2C-Properties of liquids and 2D- Properties of solids.