Helium Advantages


Helium mass spectrometry, or helium leak testing, is a highly precise means of leak detection. This technology was first developed for the Manhattan Project during World War II to locate extremely small leaks in the gas diffusion process.

At the heart of helium leak testing is a complex piece of equipment called a helium mass spectrometer. Quite simply, this machine is used to analyze air samples (which are introduced into the machine via vacuum pumps) and provides a quantitative measurement of the amount of helium present in the sample. In practice, a “leak,” is identified by a rise in the level of helium being analyzed by the machine.

Helium leak testing can identify extremely small leaks. For example, our equipment can detect a leak so small that it would emit just two cubic centimeters of helium (or the amount equal to two sugar cubes) in 320 years. While very few applications require this level of precision, this example serves to highlight the accuracy possible with this process.

While helium leak detection may appear to be a simple procedure, the process involves a combination of both art and science. The user must ensure the equipment is functioning properly and the process is highly dependant upon the user’s experience. Consider this analogy: while anyone with enough money can buy an airplane, learning how to fly one takes a lot of practice. The same is true with helium leak detection—make sure your “pilot” knows how to fly.

Why Helium Is Superior

While many gases are used in leak detection, helium’s qualities provide for superior testing. Having an AMU (Atomic Mass Unit) of only 4, helium is the lightest inert gas. Only hydrogen, with an AMU of 2, is lighter than helium. However, due the hydrogen’s explosive potential it is rarely used.

Additional reasons why helium is a superior tracer gas:

  • Only modestly present in the atmosphere (roughly 5 parts per million)
  • Flows through cracks 2.7x faster than air
  • Nontoxic
  • Nondestructive
  • Nonexplosive
  • Inexpensive
  • User Friendly
Due to these attributes, and its high sensitivity, helium leak testing has gained broad acceptance in a wide range of leak testing applications.

Helium Leak Testing’s Two Primary Testing Modes

While there are a variety of testing procedures, in general there are two primary methods of helium leak testing:


Spray Probe

The leak detector is hooked directly to the system under test and the inside of the system is evacuated. Once an acceptable vacuum is achieved, helium is sprayed discreetly on the outside of the system, with particular attention being paid to any suspect locations.

Sniffer Probe

Helium is purged throughout the inside of system being tested. Due to the innate properties of helium it readily migrates throughout the system and in its attempt to escape penetrates any imperfections, including: defective welds (caused by cracks, pin holes, incomplete welds, porosity, etc.), flawed or missing gaskets, leaks due to loose clamps, or any other defect.


The choice between these two modes is based on both the size of the system being tested, as well as, the level of sensitivity required.

Specialized Testing Techniques

In addition to the two primary testing procedures listed above, there are a number of more specialized techniques that can be utilized. Among these techniques, we routinely employ bagging or hooding and bombing.