Leak detection systems may be classed according to three typologies, each functioning according to its own method:

• systems based on pressure variations over time;

• devices for determination (detection or localization) of leaks, based on physical principles of varying complexity, which turn the flow of simple air through the leak aperture into a visible, audible or, in any case, monitorable phenomenon; among these, we have ultrasonic measurement systems and the bubble test;

• systems which use tracer gases (generally helium), detected by means of thermal devices, electrochemistry devices and mass spectrometry