by George Irvine
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.
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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