Refrigerants are substances used in cooling systems, such as air conditioners and refrigerators, to absorb and release heat, enabling the refrigeration cycle. These chemicals can be found in various states (gaseous or liquid) and types, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and natural refrigerants like ammonia and carbon dioxide. The choice of refrigerant impacts the system's efficiency, environmental footprint, and compliance with regulations.