A test to determine the maximum Diameter of pore in membrane. openings of a filter. The differential gas pressure at which a wetting liquid (usually water) is pushed out of the largest pores and a steady stream of gas bubbles is emitted from a wetted filter under specific test conditions. Used as filter A non-destructive test which is used to predict the functional performance of a filter. The valid use of this test requires that it be correlated to standardized bacterial or particle retention test. Examples: Bubble Point Test, Diffusion Test, Forward Flow Test, Pressure Hold Test.... with specific, validated, pressure values for specific pore-size (and type) filters.