Clarification of Answer by
24 Feb 2005 03:22 PST
I'm skeptical for several reasons:
1. I doubt the absorption of oxygen story. Jumpers with a helmet
would have virtually no skin area exposed.
2. suffocation would take several minutes. A skydiver's terminal
velocity is 172 feet per second -- or 10,300 feet per minute. Clouds
exist that are that thick -- but not clouds that jumpers would be
The Physics Factbook
"Speed of a Skydiver (Terminal Velocity)" (undated)
More worrisome to jumpers would be hypoxia, which would start in the
aircraft cabin on the ascent. Most people start to show signs of
hypoxia above 7,000' and will have blood oxygen saturation levels drop
below 90% -- not a dangerous level but one which slows thinking.
According to "How Stuff Works," oxygen isn't required below 16,000'
for skydivers. Even then the jumper would be in freefall for no more
than 75 seconds:
How Stuff Works
In trying to assess the skin absorption issue, I used a Google search strategy of:
skin absorption of oxygen
The National Institute of Occupational Safety & Health (NIOSH)
indicates that WHOLE body absorption of oxygen is only 10% of that
provided by the lungs:
"System Toxicity from Skin Exposures" (McDougal, Sept. 8-11, 2002)
Obviously high speeds increase the air pressure -- but ambient oxygen
levels are lower (half at about 18,000') and little skin is exposed
during a jump.
This is really an aside, but a friend who trained for high-altitude
balloon flights once told me that the significant risk in jumping in
an emergency wasn't hypoxia -- they were prepared for that. Rather,
in jumping from an airplane the skydiver has the speed to be
aerodynamic and control body position. However, in jumping from the
balloon capsule the skydiver may start to tumble, which is both
disorienting and which makes chute deployment more risky.
I hope that this helps in settling the issue. Often one runs into
bizarre assumptions, like the one from rec.skydiving. I have a book
on my shelf that claims that there's less oxygen at night, a factor
that the author contends had contributed to plane crashes. It's
nonsense but there's a small grain of truth to it: flying at night
relies on visual acuity and one of the first senses to be effected by
hypoxia is vision. Light is much dimmer.
So, while there's NOT less oxygen at night, it IS more important for
pilots to be using it.