Carbon dioxide is a colorless, odorless, non-toxic, odorless, chemically stable and inexpensive gas. It is liquid under normal temperature and pressure, and its density is higher than that of air (about 1.3). It can dissolve in water to form carbonated beverages; it is easy to liquefy and release a lot of heat; when it is burned, it generates water and carbon dioxide. CO2 compressors take carbon dioxide, which is a gas at normal temperature and pressure, and apply high pressure to become a fluid in a critical state. The fluid is sent to the area that needs to be cooled, and the fluid evaporates and absorbs a lot of heat, thereby achieving cooling.