Part I: Defining The Dye Ingress Operating Window

Dye ingress testing remains a familiar approach for evaluating container closure integrity in prefilled syringes and other parenteral systems, yet its performance depends on a sequence of mechanical and physical events that aren’t always stable or predictable. Effective testing requires both the creation of a sufficient pressure differential and the ability to maintain that differential long enough for dye to move through a defect. In liquid‑filled syringes, however, factors such as viscous resistance, capillary forces, and plunger compliance significantly influence system behavior. As product viscosity rises, defects shrink, or syringe diameter increases, the operating window for successful dye ingress rapidly narrows.

Explore how these limitations can undermine consistency and raise important questions about the suitability of dye ingress as a reliable CCI method for high‑risk parenteral applications.