Since gas is compressible, pressure (or vacuum) influences the extent of the leak, so leak rates are expressed in mbar * l / s, where the "leak rate" is the amount of gas that flows through a leak at a certain time and pressure differential per time.
Leak rate calculations start with the following: The leak's diameter is circular and the leak channel is equal to the thickness of material the leak "passes through". There are many methods and standards for leak detection and detectors. Avail more details about leak and packaging testing methods via https://flexpakinc.com/test-methods/.
DIN EN 1330-8 is one of the standards that govern leak detection and leak detection. It describes the "helium standard leak rate" where helium is used to test for leaks at pressure differentials of 1 bar from external atmospheric pressure to 1 mbar inside pressure. These conditions are very common in practice.
Manufacturers must ensure that their products are leak-free in accordance with safety and environmental standards. Leak testing is required as part of quality approval/production.
To determine the rejection rate of a test with helium under standard conditions, it is necessary that the test conditions be converted to standard conditions. There are standard formulae for such conversions.
A vacuum system must be connected to a leak detector in order to detect helium leakage. Leak tests can be performed using helium. They are reliable and repeatable and can be measured and monitored continuously.