High purity helium means that its composition is greater than 99.999%, meaning that the impurity content is less than 10×10-6 (volume fraction) of the gas. The total impurity in pure gases supplied by industry is usually less than 100 x 10-6 (volume fraction), so the impurity must be removed by further purification to 10% x 10-6 or less.

The main impurities in industrial pure helium are nitrogen, oxygen, water, carbon monoxide, carbon dioxide, and hydrocarbons, which can be removed by nitrogen removal.

Nitrogen removal

Nitrogen removal is sometimes accompanied by deoxidation. It's mostly absorbed by metal ghettos. Commonly used metal slums are calcium, titanium, uranium, and zirconium-aluminum-16. When calcium metal is used as an getter, both nitrogen and oxygen are absorbed. The reaction temperature is 650 ~ 680℃, the impurity concentration in the intake air is 240×10-6 (volume fraction) equivalent, and the impurity in the outlet is less than 50×10-6. The utilization rate of calcium metal is 50%~60%. Impurities such as oxygen, nitrogen, hydrogen, water vapor, carbon monoxide, carbon dioxide, and hydrocarbons can be absorbed simultaneously using spongy titanium or zirconium-aluminum-16 as an getter.