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A GRADIENT OF EFFORT
In reply to Steve Borgess’ letter in
the Fall 2015 issue, conservation is
not an all-or-nothing game. Small
choices do make a difference.
I and many others make them
every day. I avoid red meat on
most days, but I occasionally
have barbeque or a steak. See
how that works? Pretending that
a gradient of effort is impossible
or implausible serves only to
maintain the cognitive dissonance
rooted in one’s own inaction.
— Matt Kofron, via email
IT’S ALL IN THE LOOP
Laurent Ballesta’s dive to 66 feet
for 24 hours employed a protocol
that used “10 percent oxygen
heliox as [the] basic mix for the
first 18 hours and almost pure
nitrogen with a small amount of
oxygen after that.” This purportedly
allowed decompression in less than
three hours for a dive that would
normally require 20 hours of deco.
How does such seemingly extreme
nitrogen loading work to minimize
decompression time?
— Phil Burgiel, Rockville, Md.
My name is Jean-Marc Belin, and
I was the diving supervisor for
Laurent during the dive to 66 feet for
24 hours. We used a dive protocol
that varied the partial pressure of
oxygen during the dive and employed
two different diluent gases. During
the first 18 hours at 66 feet, the
rebreather was programmed to
deliver a breathing mixture of helium
and oxygen with an oxygen partial
pressure of 0.49 atmospheres (ata).
For such a long dive, this was the
maximum partial pressure of oxygen
Laurent could breathe without
incurring lung damage. Helium was
used because it would involve less
of a decompression obligation than
nitrogen for the long dive.
At the 18-hour mark, the
rebreather was programmed to
produce a breathing mixture with
an oxygen partial pressure of 0.9
ata, and the helium was replaced
with nitrogen. The logic behind this
diluent switch was that the diver
would offgas helium faster than he
would ongas nitrogen, and thus the
net inert gas load would decrease.
During the last three hours of the
dive the partial pressure of oxygen
was set to 1.3 ata to speed up
decompression.
— Jean-Marc Belin, via email
TEACH YOUR CHILDREN WELL
I enjoyed the Expert Opinions
article “Children and Diving” —
it had some excellent insights.
I think everyone agrees that
establishing a diver’s comfort and
confidence in the water early,
regardless of age, is essential.
But I’m curious about the
photos. The first one shows a
young diver with an unsecured
pressure gauge. That’s not a
huge deal in and of itself as long
as she can retrieve it. The next
photo, however, shows the same
gauge rigged behind the diver’s
back and on the opposite side.
More important, there is no low-
pressure hose connected to her
BCD inflator. With a steel cylinder
and no thermal protection, she is
probably quite negatively buoyant.
I imagine the photos were
staged, but to me they set a bad
example. All beginning divers
should learn buoyancy control
early on (for a number of reasons)
as well as the need and ability to
establish positive buoyancy in an
emergency. This skill is essential
to preventing fatigue, panic
and possibly drowning. I hope
every diver is still taught how to
manually inflate his or her BCD on
the surface. At depth, an out-of-
air situation involving a negatively
buoyant diver is a much more
serious — potentially devastating
— situation.
We instill in all divers, regardless
of their age, the importance of
preparing and checking their own
gear before every dive. We guide
them through the process. Am I
missing something here?
— Mark Windham, via email
L E T T E R S
14
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WINTER 2016
FROM THE SAFETY STOP
LETTERS FROM MEMBERS
STEPHEN FRINK