Units of gas permeability constants

Gas permeability constants of polymers are generally expressed by composite units which contain Numerous combinations of various units to express each component units are used. However, permeability constants of nongaseous substances in polymer membranes are generally expressed by the units of cm²/sec, which are identical to the units of the diffusion constant. The relationship between constants in units of cm²/sec and conventional composite units for gas permeability constants is presented, and the advantage of using the units in cm²/sec to express gas permeability constants is discussed.