On Mon, 15 Aug 2005 18:36:13 UTC, T o d d P a t t i s t
wrote:

: "Ian Johnston" wrote:
:
: Oxygen is only part of it. The breathing reflex is triggered by the
: carbon dioxide partial pressure in your lungs: when atmospheric
: pressure falls below that you never get the trigger and your lungs
: just stop working. This is a Bad Thing.
:
: Your lungs work OK, but there's not enough O2 to keep you
: conscious. ...

Thanks.

: Of course, at high altitudes, if the PP of CO2 is so low
: that your body fails to breathe, then that can cause of
: death, even if the PP of O2 would be high enough to keep you
: alive.

That's what I ws thinking of. Doesn't that effect kick in about thirty
something thousand feet?

Ian