Enhanced aerosol test for assessing filter integrity

A method of integrity testing a filter in the dry state, comprising:

• providing a liquid sterilizing grade filter to be tested in a dry state, wherein said liquid sterilizing grade filter is a filter capable of totally retaining a B. diminuta challenge level of 107 cfu/cm2 at a differential pressure of 30 psi;
• generating an aerosol particle stream with at least one atomizer at a pressure of at least 5 psig, wherein the particles in said stream have a concentration of at least 103 particles/cm3 and have a size effective to penetrate a defect less than 20 μm in diameter if present in said filter but not effective to penetrate integral regions in said filter;
• challenging said filter with said aerosol particle stream;
• providing a particle detector downstream of said liquid sterilizing grade filter to detect any particles that penetrate said defect if present in said filter;
• and
• classifying said filter as non-integral if a particle is detected by said particle detector, and classifying said filter as integral if no particles are detected by said particle detector.