In article ,
Dave Eadsforth writes:
Snip - breif description of Diluter-type O2 systems

So, if you're flying through a smoke cloud from a fire, or a flak
burst, or the gun gas coming from your muzzles, you'd smell it.
(Never experienced that myself - But I do know that if you're flying
over South Dakota you can smell the cows.)

Thanks for that, Peter; I had heard of the economiser but had no
knowledge of how it worked. I did know that the early oxygen systems
were not force feed, which led to hypoxia (or anoxia - whichever term
you like best) in photo-reconnaissance pilots and less fit crewmen, but
no idea of the dilution. No wonder...

Pressure Oxygen systems aren't required until you get above about
35,000-40,000 ' (11,000 -13,000m) or so. Below that height, there's
enough pressure to force the air/Oxygen mixture through the wall of
the Aveolae in the lungs. Above that heoght, even pure O2 won't make
it into the bloodstream without some help. So, positive pressure
systems wre developed, these force O2 into the mask at higher than
ambient pressures, forcing the gas into the lungs. These systems
require masks that make a positive airtight seal to your face, and
breathing with them takes a bit of getting used to. Above 50,000',
you begin to need full-body pressurization, either from a pressure
cabin or a pressure suit.

Re. cows, has not the methane from the world's cattle been identified as
a major contribution to reduction of the ozone layer? Damn good reason
not to be vegetarian - eat more meat...and quicker...God bless Atkins...

The Greenhouse effect, mostly. Despite the jibing the Pres. Reagan
took, another big contributer is Coniferous Trees. (Pines, Spruce,
Cedar, etc.) Their pitch is high in volatile hydrocarbons, such as
Furaline (Turpentine). This will basically boil off on warm days, and
enter the atmosphere. That's how the Smoky Mountains got their name.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster