Abstract: Leak testing using a testing chamber into which a test part may be configured for testing. The test part defines a leak test boundary to be tested. Tracer gas is introduced into a first volume on one side of the leak test boundary. A vacuum (e.g., a rough vacuum) may be introduced into a second volume on the opposite side of the leak test boundary. A tracer gas permeable membrane is placed in situ within the second volume, or at least in gaseous communication with the second volume perhaps within or rigidly attached to the wall of the chamber. During testing, if some of the tracer gas introduced into the first volume were to leak through the leak test boundary defined by the test part into the second volume, at least some of that tracer gas may pass the tracer gas permeable membrane for subsequent detection.