OT Don't read this (was Re: Altair MBL source)

You're forgetting that while gases do stratify based on weight, this takes time. If you were take a lungful of a mix of gases and hold it, completely still, for a long time (hours to days), yes, it would stratify out. But the typical time between inhaling and exhaling is so short that for anything nonviscous enough to breathe, the weight of the gas doesn't matter. As someone else poinetd out, it's the same reason we don't have some miles of argon and carbon dioxide at the bottom of the atmosphere: there is constant mixing going on. This is a mystery to me. Even with no oxygen to breathe at all, a person can remain conscious for several seconds - a fairly long time when you're rushing for the exit door - and a lot longer than that with enough warning to get a lungful of good air. Sitting here typing this, I've held my breath for a minute and a half, without any more preparation that one deep breath; even deliberately stopping breathing at the empty end of a normal breath, I had no problem for fifteen seconds and only minor problem with thirty. I speculate that what happened is that this person got, by chance, a lungful with almost no air in it and panicked at the suffocating feeling, attention going to dealing with breathing rather than to getting out of there. /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse at rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B