To classify the pollution degree of compressed air is actually to classify the quality of compressed air. All walks of life for air quality requirements are not the same, in order to have a unified standard of measurement, the International Organization for Standardization (ISO) in the world for compressed air and purification equipment standardization and unification. In its series of standards ISO8573, there are generally used compressed air quality levels and various pollutants test methods.
China's national recommended standard GB/T1327 is equivalent to the ISO8573 developed.