Leak testing techniques enable to detect leaks corresponding to the leaking of one cubic centimetre gas flow in 300 years.

There are various testing techniques which can be applied:

• under vacuum or under pressure,
• with different search gas: helium, ammonia, sulphur hexafluoride,
• to closed volumes with a value varying of some cubic centimetres to thousand cubic meters.

Leak testing equipment is a type of nondestructive testing equipment used to measure the escape of liquids, vacuum or gases from sealed components or systems. Some configurations require a separate leak detector or sensor as an input. They are often equipped with various other components such as pumps, calibrators, gages and cases. A leak is a hole or porosity in an enclosure capable of passing a fluid from the higher pressure side to the lower pressure side. There are many basic leak test methods and a few variations. The most familiar are dunk testing, pressure decay, mass flow, mass spectometer and ultrasonics. Dunk testing is still the most popular method, with pressure decay and mass flow rapidly gaining in use. Mass flow is the de facto test method of choice in automotive applications. An exception is pressure decay testing on a brazing fixture.

If there is a situation where a no leak application is required, there is only one choice— mass spectrometer—regardless of cost. This application uses helium and hydrogen gases as part of its inspection process. The good news is the leakage may be so microscopic it is rarely detrimental to product performance.