This document specifies a bubble-point test method applicable to filter elements used in hydraulic fluid power systems. It can be used both to verify the fabrication integrity of a filter element (by checking the absence of bubbles) and to permit the localization of the largest pore of the filter element by determining the first bubble point. NOTE Verification of fabrication integrity is used to define the acceptability of the filter elements for further use or testing. The first bubble point is established through continuation of the fabrication integrity test. It is under no circumstances a functional characteristic of a filter element; in particular, it cannot be used to estimate filtration rating, efficiency or retention capacity and is intended to be used for information only. This document specifies a method to normalise fabrication integrity and bubble point data to a standard value of surface tension when test fluids other than 2-propanol are used.