The Bubble Point specification provided on the Certificate of Test is a manufacturing specification for the filter membrane and should not be used by the end-user as a test limit for the final device. The Manufacturing specifications limit value relies on a defined endpoint and is therefore has a defined end-point.  This uses a different Bubble Point test method than what the end-user performs (which inherently is more  subjective).


Pall provides a certificate of test with each sterilizing grade filter. The first paragraph Certificate of Test discusses the membrane Bubble Point.  An example of this statement is as follows: The 0.2 µm filter membrane used in the filter element has a quantitative bubble point (i.e. "KL") which met or exceeded 3655 mbar (53.0 psi) in water.


As stated, this value is the minimum specification of the flat sheet membrane that is used in the device, not the specification of the device itself.  This test, termed the Quantitative Bubble Point (QBP), is objectively and quantitatively defined as the pressure needed to achieve a specified air flow limit through a specified membrane area.  This test is conducted on samples from every sterilizing grade membrane roll produced by Pall and reflects the largest pores in each entire roll, to be used either in discs or in cartridge production.


The minimum expected Bubble Point (BP) limit provided for cartridge filters are typically lower than the minimum membrane QBP. The lower end-user Bubble Point limit considers the lower observed Bubble Point typically seen with increasing filter area. It also considers the variability in BP measurements due different algorithms used by different test instruments, as well as variability due to human interpretation of the test result when a visual (manual) Bubble Point test is used.

Please contact Pall Corporation if you require minimum Bubble Point test parameters.