The Millipak are 0.22 µm membrane filters designed as a safe and efficient barrier against particulates and bacteria. The Millipak devices use the unique, clean stacked disc design that eliminates the risks of particulate-producing woven downstream support found in many pleated membrane capsules. The 0.22 µm filtration membranes used in the Millipak have been validated for bacteria removal following the HIMA rules, using a challenge with Pseudomonas Diminution at 107 organisms / cm² of membrane. The bacteria retention efficiency has been correlated during validation studies with the non destructive bubble point and air diffusion tests in order to allow the verification of bacteria retention for each device at the end of the manufacturing process.