Leak detectors can be used to locate leaks or are suitable for determining leak rates of test objects.
The tightness of a component or system depends on the intended application and the acceptable leak rate. There are no absolutely leak-free components or systems. A component is considered technically leak-tight if its leak rate remains below a specified value for these components.
In addition to determining complete tightness, it is usually important to localize leaks quickly and precisely in order to seal them. Instruments used for local leak detection are called leak detectors.
In practice, the leak detector performs this task by first evacuating the part to be tested so that gas can enter from outside through the existing leak due to the pressure difference. If only helium is directed in front of the leak (e.g. with a spray gun), the helium flows through the leak and is extracted by the leak detector. The partial pressure of helium in the leak detector is measured by a sector mass spectrometer and displayed as the leak rate. This is usually indicated as the volume flow of helium (PV flow).