A supercritical fluid is any substance at a temperature and pressure above its critical point. It can seep through solids like a gas, and dissolve materials like a liquid. plus, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties of a supercritical fluid to be negligable. Supercritical fluids are used as a substitute for organic solvents in a range of industrial and laboratory processes.
Carbon dioxide is the most commonly used supercritical fluid. they are used for decaffeination. It is a gas at standard temperature and pressure.