Q & A Post 38.08.18
Q: How would you establish the load composition for half and full cycles, especially for dunnage pallets which do not contain BIs? I remember reading in a standard or TIR where "PVC" was mentioned as a highly adsorbing material. Accordingly it would sound like a valid approach to take pallets of maximum pallet density. Another (cheaper and easier) approach might be using random scrap material from production with maximum pallet density.
A: 1) Based on your question, and for those who read this, I think it’s important to clarify that you are referring to ethylene oxide (EO) sterilization. 2) The load composition for the qualification runs should be established using a worst-case scenario with regard to both density and absorption (of EO, temperature, and humidity). Also, don’t forget to consider maximum and minimum loads if applicable. 3) Whether the qualification load is comprised of all dunnage, all saleable product, or a mixture of both, and assuming that you are doing an "even" geometric BI distribution throughout the load, all pallets should have BIs, including dunnage pallets. 4) How much EO is absorbed (and adsorbed) compared to other plastic materials is somewhat of a subjective call, but personally I would not classify PVC as a "highly adsorbing material," but I might call it an “above average" on its relative absorption (and adsorption) properties as compared to other polymers. (Please be mindful that when PVC is sterilized with EO, ethylene chlorohydrin (EC) residues should be carefully considered as PVC may have elevated levels of this compound.) 5) Caution should be exercised if using “random scrap material from production with max. pallet density,” to ensure that it mimics the characteristics of the actual products being processed, that it is actually worst-case with regard to density and absorption (see above), and that it is not so “worst-case” that its use results in undue time and expense.