Heliumrich

Heliumrich is a term used to describe a substance, environment, or object that contains a high proportion of helium relative to other constituents. The expression is not a formal scientific designation but a descriptive label applied across several fields to indicate elevated helium content.

In gas mixtures, helium-rich compositions are used for inerting, leak testing, cryogenics, and certain welding processes. Helium is often paired with oxygen or nitrogen, and compositions are described as helium-rich when helium exceeds the proportion of other gases—commonly above 50% by volume. In diving, helium-rich mixtures such as heliox and trimix reduce nitrogen narcosis and oxygen toxicity at depth and are chosen based on depth and risk considerations.

In astronomy, helium-rich atmospheres appear in some classes of stars, notably hot helium-rich subdwarfs and white dwarfs with helium-dominated photospheres. These objects show prominent helium lines and are studied to understand diffusion, radiative forces, and late-stage stellar evolution.

In planetary science, helium is a major constituent of the outer atmospheres of gas giants, though the use of the phrase helium-rich is not standard for describing whole planets; researchers may refer to layers or regions with enhanced helium abundance due to processes like fractionation or atmospheric escape.