To what extent the conventional gas permeation testing method is reliable for membrane systems?

• A critical review on the conventional gas permeation testing (GPT).
• Determining shortcomings of the conventional GPT.
• Applying the conventional GPT leads to erroneous predictions.

This work intends to analyze the inaccuracy which appears in the predictions of the conventional gas permeation testing (GPT) method. A theoretical combined with an experimental analysis were presented to study the capability of the conventional GPT method with reference to the membrane structural parameters. Although, the conventional GPT method is relatively easy and fast to be implemented, it normally prone to some inaccuracy caused by inadequate experimental and theoretical techniques. Therefore, it suffers from several conceptual drawbacks. In comparison to the Wakao et al. model, it can be concluded that the modified rp and (ε/lp) were different from the conventional one by a factor of 3π/16, and (16/3π)2 respectively. In addition, depending on which part of the J versus P is selected, different rp and (ε/lp) will be resulted in. Finally, at the regions which the slope is negative or zero, the conventional GPT method is not capable to establish any prediction.