Trace gas helium for leak testing

The helium leak test is based on the detection of helium as the test gas, which only occurs in the ambient air in a very low natural concentration of approx. 5 ppm. Therefore, a reliable test statement is possible even by detecting a small amount of helium. Before a helium leak test, a rough leakage measurement is usually carried out first.

The test chamber is evacuated and the test specimen is pressurised with helium. Helium escaping through leaks is sucked in by a high vacuum pump and detected.

The test specimens are either filled with helium before sealing or subsequently subjected to helium overpressure for a certain time so that helium penetrates the test specimen. This is followed promptly by testing in a vacuum test chamber, where the amount of escaping helium is determined. A mass spectrometer, which consists of an ion source, the separation system and the ion detector, serves as the detection system for the test gas.

Tracer gas Helium

  • Occurs in nature only atomically, builds no molecules. Chemically inertly due to its (only) completely occupied valence electron shell.
  • After hydrogen the secondly most frequent element in the universe.
  • Natural gas contains on the average 0,4% He and is thereby the economically most important source for the helium production.
  • By all gases Helium is the most difficult to liquefy and cannot be converted in solid state at normal pressure. At 30 bar: Freezing point -271.4 °C; Boiling point at normal pressure is -269 °C.
  • Density (20 °C): 0.1664 gram/liter
  • Mol mass: 4.003 u (small, light molecule, which passes easily small leakages)
  • moderate price for industrial applications


Some applications of helium:

  • Inert gas for welding light metals and alloys
  • filling gas for balloons
  • additive to the breathing air when deep diving against the diver´s palsy
  • Medical technology; in case of breathing problems
  • Ion beams from Helium nucleus to mediate eye or cerebral tumors


Some more trace gases

Other test gases for the leak test are e.g. hydrogen and SF6.


We are using cookies.

We are using cookies on this web page. Some of them are required to run this page, some are useful to provide you the best web experience.