There are numerous scientific studies that show a helium-based test method is the optimal leak testing solution for glass vials fitted with rubber stoppers and crimped seal. This approach has shown that safer, lowers limit leak rates of microbial ingress can be established for parenteral vial closure systems. These studies used calibrated laser drilled holes, copper wires to impact the rubber seal as well as the creation of defects in the actual glass vials. The results consistently show that the helium leak rate was a function of the square of the hole diameter and fit well with theoretical calculations. Comparison with the microbial challenge showed that for micro holes a lower size limit was found to be 2 μm with a corresponding leak rate of 1.4 x 10-3 mbarl/s. For the fine wire experiment the lower limit was 15-μm wire and a corresponding leak rate of 1.3 × 10-5 mbarl/s. From these tests a safe, lower limit, leak rate was established.
REFERENCE: Leak Testing in Parenteral Packaging: Establishment of Direct Correlation between Helium Leak Rate Measurements and Microbial Ingress for Two Different Leak Types