In this paper, we are introduced to the counterclockwise cooling cycle, and three ways to improve the cooling cycles are described. Refrigeration cycles use refrigerants to transfer heat energy. The refrigerants are divided into five basic groups, each group is described and the method of labeling the refrigerants is shown. Some refrigerants affect the environment, so the global warming potential (GWP) and ozone depletion potential (ODP) are very important characteristics for refrigerants. In the late 20th century, scientists discovered an ozone hole in Antarctica, and a decision was made to reduce the use of ozone-depleting substances. The most significant protocol that reduced the use of substances was the Montreal Protocol, followed by the Paris Agreement and the Kyoto Protocol. The goal of these international protocols is to reduce global warming significantly below 1.5 ° C and completely eliminate ozone-depleting refrigerants. The second part of the paper presents the properties that new replacement refrigerants must have, namely: non-corrosivity, non-toxicity, non-flammability, high critical and low triple point, high volumetric cooling effect, minimal impact on the environment, etc. New refrigerants are divided into three groups: chlorine-free, low-GWP, and halogen-free. Furthermore, some of the substitutes are described and their most significant properties are shown in the table.