inert gas 
noun
Another term for noble gas.Krypton is the fourth member of Group 18 of the periodic table, a group of elements known as the noble gases or inert gases....
- Fluorine gas, diluted with an inert gas such as nitrogen, can now be used to fluorinate selectively a range of systems by simply passing this gaseous mixture through a cold solution of the substrate in formic or other acid.
- Natural gas contains other compounds than hydrocarbons, including significant quantities of gases such as carbon dioxide, nitrogen, and hydrogen sulphide and traces of inert gases such as helium.