As environmental temperature and pressure changes, any kind of material phase - there are three kinds of gas phase, liquid phase and solid phase, the coexistence of three other equilibrium point is called the triple point. Liquid, gas two phase interface state point is called supercritical point. When the critical point of temperature and pressure is known as a critical temperature and critical pressure, different material the critical point of different pressure and temperature. Super Critical fluid (SCF) refers to the fluid whose temperature and pressure are both higher than its Critical point. The supercritical fluid commonly produced is carbon dioxide, ammonia, ethylene, propane, propylene, water, etc. When an object is in a supercritical state, because the gas-liquid phase properties are so similar that it cannot be clearly distinguished, the article named "supercritical fluid" comes from the network

Carbon dioxide extraction