Helium is a non-flammable, colorless, odorless gas which is the second lightest element know. Its concentration in the atmosphere of just 0.0005% also makes it one of the most rare gases. Natural gas wells store helium and provide the principle source of this gas, which is extracted by a stripping process.

After hydrogen, helium has the smallest molecular cross-section of any gas. Its permeation rate and ease of detectability make it an ideal medium for leak detection.

Helium is widely used as a shielding gas for arc welding and as an inter gas in the production of reactive materials, and safely fill the need to replace hydrogen in lighter-than-air applications. Helium is also used for balloon filling.