They say that regardless of altitude the % of individual gases stays the same? (excepting ultra high extremes perhaps)
true/false?
Clarify:
At sea level O2 is 23 % then at 6000 meters it is still 23%
true / false?
In Denver (1609 meters) the O2 in the atmosphere would still be 23%
true /false?
If true then :
If that percentage of O2 was only 21% at sea level then Denver would record 21% as well...
so reduction of % at sea level will display at any altitude ( exception to ultra high perhaps )
A reduction recorded of O2% at JUP or FJF research stations would reflect at all altitudes ( assuming minor corruption of data due to local conditions)
So whilst O2 "quantity" may reduce at high altitudes ( Denver ) and is tolerable due to acclimatization of the population the percentage O2 in the ambient air available is the same as at sea level.
Do you see the difference (context) in what we are referring to or do I need to go on....
Have I got it correct so far?
You are correct. Insofar as altitudes at which people live, the percentage is the same.
But quality of air is important too.
In some densely populated cities the oxygen percentage can be as low as 12%