Preliminary Engineering Assessment of Condensation Risk and Aeration Performance in Vaporized Hydrogen Peroxide Decontamination of a Pharmaceutical Isolator

This paper presents a preliminary engineering assessment of a VHP decontamination cycle in a pharmaceutical isolator by converting available process observations into measurable indicators, namely initial humidity margin, maximum injection-stage relative humidity, hydrogen peroxide concentration response, and apparent aeration performance. The observed cycle began at 26°C, 45% RH, and 0ppm H2O2. A 60 min dehumidification stage reduced the chamber humidity to approximately 17% RH and increased the chamber temperature to about 37 °C. During VHP injection, the maximum relative humidity was 50.58% RH, while the hydrogen peroxide concentration reached 480 ppm with an average value near 400 ppm. These values indicate that bulk condensation risk was minimized under the tested drying condition. In contrast, the aeration stage remained the main engineering bottleneck. After 60 min of aeration, the hydrogen peroxide concentration decreased only to 68 ppm, which is still above the target of less than 1 ppm. Based on an inlet velocity of 0.45 m/s, an estimated inlet area of 0.031m2, and a chamber volume of 1 m3, the airchange rate was approximately 50.22 h-1. The discrepancy between this high nominal air exchange and the remaining H2 O2 concentration suggests non-ideal removal caused by adsorption, desorption, filter retention, or dead-zone effects. The results support the use of RH-based injection permissive and residual H2 O2-based aeration termination criteria for future cycle improvement.