How do I determine the required amount of breathable area of a package?
Total package porosity, which is a function of gas flow and surface area, is critical to the sterilization and aeration phases of Ethylene Oxide (EO) gas sterilization processes. Whether designing a port, the size of a secondary label or optimizing a cycle, there is no generic answer for all packages and types. The general rule, of course, is that more porosity is better. In other words, as the porosity increases cycle and aeration times can be reduced, and a smaller porous area maybe sufficient. However, all are package, product and cycle dependent.
Without knowing the details of a specific application it is hard to predict the required porosity of an individual package design. Theoretical calculations for porous area require knowledge of some key package and cycle characteristics. Breathable surface area, package volume, secondary and tertiary packaging, and peel force are all factors which determine porosity limitations. Information regarding the worst case average porous area, the volume of the package, and the gas exchange rate for each part of the ETO cycle at a minimum is needed. Even though there have been several attempts to create such predictive models, in the end sterilization testing is still required to qualify a package design. Product families of worst case configurations and cycles are helpful to limit the amount of testing, but optimization of package porosity for an ETO cycle is often an iterative process.