(UTC) 

 ::::::The reactivity or inertivity (new word?) of a gas has little do with the narcotic effect. Also, this effect changes at different mixtures and pressures. Both inert and reactive gasses have such an effect, even pure oxygen. The exact mechanism is unknown, but some think, in the case of nitrous oxide or xenon, that it dissolves in the blood and causes displacement of oxygen. It is interesting to note, that some gasses are *less* narcotic than air (apparently). Building a table of the exact narcotic effect at any pressure would probably end up a phase diagram for every gas. In the safety section of helium, one might mention only, that it is less narcotic than air, oxygen, or nitrogen. (Those kids who got suspended for sniffing helium at a school, under the school's zero drug tolerance law, could take that bit of info to court)  21:53, 9 Apr 2005