The Bubble Point Test is designed to detect the largest pores of hydrophilic and hydrophobic membrane filters.  The Bubble Point test is based on measuring the gas flow across a completely wetted membrane at increasing gas test pressure, until the point at which the wetting fluid is expelled from the pores, and bulk flow is measured. 

The Bubble Point test is considered a subjective test, and the results can vary depending on the algorithm of the test instrument.  The Bubble Point method is the preferred integrity test method for testing filter discs, as the Forward Flow is often too low to be accurately measured.