x1=t1=g1 is inert gas of material/composition including x2=g2, under conditions x3=g3.
Inert gases are different from noble gases both in the intension and the extension. Noble gases, nitrogen gas and some compound gases are called inert gas depending on context, though some heavier noble gases, as well as nitrogen, react with other substances under certain conditions. See to'e frati gapci; navni.