inert gas
gas which does not undergo chemical reactions under given conditions
shielding gas
inert or semi-inert gases that are commonly used in several welding processes
noble gases
group of chemical elements in column 18 of the periodic table, that tend to be chemically inert and thus form odorless, colorless, monatomic gases with low reactivity; consists of helium, neon, argon, krypton, xenon, radon, and possibly oganesson