Influence of Leak-path Length on the Leakage Rate for Package Integrity Evaluation

In order to improve package integrity testing for sterile pharmaceutical products, the effect of leak-path length on leakage rate was analyzed using the modified Knudsen equation, which is applicable irrespective of the gas flow regime through small holes serving as leak paths. The calculation results clearly showed that the leakage rate decreases as the leak-path length increases, indicating that the values presented in USP <1207> are valid only for very thin packages. This relationship may provide valuable information for establishing a product-specific maximum allowable leakage limit (MALL) from a more realistic perspective, as well as for selecting an appropriate test method.