The purpose of this study was to assess the impact of residual vapor phase hydrogen peroxide (VHP) on proteins and consequently establish acceptable operational limits for the commercial Isolator VHP decontamination/aeration cycle. The study was designed on the Aris test isolator to mimic process conditions: Empty syringe components were exposed for pre-determined times; product was filled into VHP exposed components; and filled syringes were exposed for pre-determined times before stoppering. Four residual VHP levels were matrixed with three exposure times for each step. The VHP concentration was continuously monitored online with the Aero-Laser. There was no impact to aggregation, clipping, purity, degradation, visible and sub-visible particle formation within the tested VHP exposure ranges. Increase in oxidation was seen for both Met257 and Met433, not only with increasing VHP levels, but also with increasing pre/post-exposure times for the same VHP level. The study was critical to identify the operational range and control parameters for the Isolator decontamination/de-aeration cycle, component prep and filling.