Qualitative leak detection initially only determines whether or not there is a large leak in the system under investigation. This is already possible from an inlet pressure of 100 mbar with the Busch TAPIR HL 2216 A. As the inlet pressure decreases, typically at 25 mbar, leak detectors are able not only to detect leaks but also to quantify them. This means that the size of a leak can be accurately determined based on the leakage rate.