inert gas

https://doi.org/10.1351/goldbook.I03027
A non-reactive gas under particular conditions. For example, nitrogen at ordinary temperatures and the noble gases (helium, argon, krypton, xenon and radon) are @U06567@ toward most species.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2196 [Terms] [Paper]