container-closure integrity test

A container-closure integrity test checks that a package actually keeps the outside world out — that a sealed vial, ampoule, syringe, or blister has no leak path letting in microbes, moisture, or gases. For a sterile product, the seal is the last line of defence, so confirming there is no hidden gap is critical.

Methods fall into two broad families. Deterministic methods directly measure a physical leak signal and give quantitative, repeatable results — examples include helium leak detection, vacuum or pressure decay, and high-voltage leak detection. Probabilistic methods, such as the microbial immersion (challenge) test or dye ingress, rely on whether a tracer or organism gets in, and are more variable. Regulators increasingly favour validated deterministic methods for sterile products and accept integrity testing as an alternative to the older sterility test for monitoring containers over shelf life.

Integrity is judged against a maximum allowable leakage limit linked to keeping the product sterile and stable, not simply pass or fail by eye. It is used in development to select packaging, in validation, and in ongoing stability monitoring, because seals can degrade or shift with temperature cycling, transport, and time.