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The big risk in gas diving is breathing the wrong gas. The WKPP
developed as part of its overall system a simple methodolgy for
preventing this.
Bottles are marked horizontally on either side in the orientation of the
diver as to the maximum operating depth of the bottle in three inch high
numbers. It's that simple.
Since "20" can look like "70" the 20 foot bottle is also marked "OXYGEN"
horizontally under the "20" (not necessary in the metric system). The
diver's name is also on the bottles.
With thousands of man dives of decompression results in the field, we
settled on standard decompresion gasses: oxygen from 20 feet, 50% oxygen
from 70 feet, 35% oxygen from 120 feet, and 18% oxygen from 240 feet for
deco, with all gases conforming to a minimum standard of 120 feet AED
and 1.6 maximum ppo2 for deco ( with 100 AED and 1.4 maximum ppo2 for
diving ). Bottom tanks are labeled for maximum operating depth as well.
There is no excuse for not permanently and properly marking bottles no
matter what gas is used. It is your life we are betting. Painted numbers
can be knocked off with a swipe of PVC cleaner, and new ones painted on
instantly. Tape can be used also, but nothing should be on the tank as
to the contents other than the MOD and the dated analysis. Clean,
uncluttered tanks are safer. They say a lot about the person diving
them.
With the tanks correctly marked, we fill them according to the following
regimen. Two pieces of tape are placed on the empty tank. After adding
one gas, but before disconnecting it from the whip, one tape is marked
with the date and the gas psi just added. The whip is removed and the
next gas added. The same proceedure is followed, marking the addition of
the gas. The tank can then be analyzed if heliox or to see what the
helium percent is by getting the oxygen percent, or the tank is topped
with air. At that point the tank is analyzed and the analysis is written
on the other piece of tape along with the date, the first piece of tape
is then used to cover the tank valve mouth indicating a full tank.
For all tanks the analysis is left on until ready to dive, but can be
removed at that point since the identification is by MOD only. Doubles
whether used or not and unused stages must re-taped and dated as to
analysis for travelling and storage. More smart people have been killed
by failing to observe this rule than any other. To keep it simple, don't
dive anything that does not have a current analysis. When in doubt,
check it out.
With MOD it makes no difference where the bottles are located on the
diver, but there should be no effort to identify a gas by its position -
this leads to error. Both the diver and his buddies whould be able to
clearly see the MOD of the gas being breathed as a check on each other.
The correct proceedure when ready to breathe a gas is to locate the
correct bottle by the MOD, remove the reg, place that reg around the
neck and into the mouth, then go back and re-locate the correct bottle,
and turn it on. IF YOU CAN BREATHE, YOU ARE BREATHING THE RIGHT GAS.
All bottles are turned off and the regs parked on the bottle when not in
use - ALWAYS. This also makes buddy idenfication of your breathing gas
easier in wreck diving where all bottles are carried. In cave, we NEVER
carry a bottle past its MOD. Trying to maximize PPO2 past a detph for
purposes of fear of decompresion is too stupid to comtemplate given the
risk assumed in the process.
If you can not see the bottle, and can not identify the gas, you DON'T
breathe it. You stick with what you know is ok until you can make a
positive id. Missing a litle deco gas is better than dying. Betting on a
system where any error cound have been made ( like putting the wrong
cover on a reg ) is inadequate for life bets.
All of our regs look the same - we do not take the chance of trying to
code regs for gases . This allows putting the wrong reg on the wrong
bottle, or the wrong cover on the wrong reg, among other things. It is
akin to loading one gun with blanks and one with real bullets, and then
trying to identify them in a dark closet before putting one to your head
and pulling the trigger. Sound preposterous? This is exactly what you
are doing if you code regs in any way. Oxygen kills you as dead as any
gun.
On a more practical note, we leave our second stages hand tight on the
hoses so we can change them out if one starts freeflowing. This way the
main regs can be replaced with the stage regs ( which bottles are turned
off anyway until used), and then the stage regs switched around to
provide something that works without killing the dive. This is SOP on
long dives. This identical reg business also prevents any problem of
switching seconds before a dive and then forgetting about it.
With the back gas , ALWAYS our deepest gas, we can always identify those
regs. The backup is hung around the neck in the DIR system, and the
other is attached to the long hose - both easy to identify. In cave
diving, we do not carry a gas through or past it rated depth. You can
see that for ocean diving , keeping the bottles turned off is the next
best thing .
You can see that in teaching gas diving of any kind, the convenience of
the MOD check on each other becomes paramount. Trying to id a student's
gas by little labels, stickers, or a plethora of "nitrox " banners or
little markings everywhere with reg jackets and colors and bands is not
going to make it safer - it is going to make it a mess. I know that
Jarrod Jablonski, in his trainging agency, GUE ( Global Underwater
Explorers ) uses the WKPP method, as he should , he helped develop it
and uses it in all of his diving.
Part of what makes a great system like this work is the ease of working
it, and the perceived benefits thereof. The GUE/WKPP method requires
doing nothing that takes you out of your way at all - it is just there,
and provides so many solutions. Long drawn out convoluted sytems break
down in action and never work underwater, and in the end get discarded
or poorly observed. This one is not only easy to do right, it is
self-correcting in that it only falls together one way - you either do
it or you do not know what you've got.
Efforts to complicate and "technify" diving make it more dangerous. Try
a little simple logic.
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