What is SSI's "Decompression Diver" course?

[Martijn]

TDI Decompression Course prerequisites:​

• Minimum age 18
• Minimum certification of SDI Advanced Adventure Diver, Advanced Diver, or equivalent
• Proof of 25 logged open water dives

8.9 Required Equipment
The following equipment is required for each student: 1. Primary cylinder(s), cylinder volume appropriate for planned dive and student gas consumption

Cylinder, with the s between parentheses

 

[CAPTAIN SINBAD]

???
Here in Europe, for these "light deco" recreational dives, we mostly use a 15 liters single tank WITH TWO VALVES AND TWO COMPLETE REGS.
Hence, in case a regulator has problems, we close its valve and use the other reg for ascending.
An octopus is considered bad practice and not safe enough here.
Still a single tank with two complete regs is not considered tech.
Some wealthy guy here also use a small twin tank, such as 7+7 liters, which is lighter and more compact than a single tank of 15 liters.

In that case it is understandable as TDI Intro to Tech also gives you the option of using deco with a single tank provided you have two valves and two complete regs. I am not sure if SSI Deco course has that because when we use the word "recreational configuration," I would assume a singe valve.

 

[inquis]

Rather than 40%, my extra cylinder is back gas.

I think this is the smarter/streamlined approach for the "light deco" scenario. Redundancy at any depth (if needed) and otherwise unused (deco from backgas, so no refill needed).

 

[CAPTAIN SINBAD]

TDI Decompression Course prerequisites:​

• Minimum age 18
• Minimum certification of SDI Advanced Adventure Diver, Advanced Diver, or equivalent
• Proof of 25 logged open water dives

8.9 Required Equipment
The following equipment is required for each student: 1. Primary cylinder(s), cylinder volume appropriate for planned dive and student gas consumption

Cylinder, with the s between parentheses

Single tank deco is totally fine as long as you are configured the way Angelo Ferina mentioned. TDI Intro to tech manual goes further into explaining that configuration with the H valves for exactly this same purpose.

 

[scubadada]

I think this is the smarter/streamlined approach for the "light deco" scenario. Redundancy at any depth (if needed) and otherwise unused (deco from backgas, so no refill needed).

And, I am by myself, nobody to share gas with. The SSI course stipulates diving with a buddy.

 

[johndiver999]

I think this is the smarter/streamlined approach for the "light deco" scenario. Redundancy at any depth (if needed) and otherwise unused (deco from backgas, so no refill needed).

I agree a lot with this. How much reduction in deco is generated from using a 40% mix versus a 32% in the bailout bottle? Say from a 10 minute deco penalty?

I have no software to answer the question, but I would assume/guess that the rich mix would shave less than 3 minutes of deco. That seems like a bad trade off in the risk/reward category. If that is what an agency is teaching, I would really like to hear the logic in how they defend that guidance.

Perhaps they just assume you are really not going to tox out at 130 on 40% for a while, and assume the diver will initiate an immediate ascent?

 

[L13]

I agree a lot with this. How much reduction in deco is generated from using a 40% mix versus a 32% in the bailout bottle? Say from a 10 minute deco penalty?

I have no software to answer the question, but I would assume/guess that the rich mix would shave less than 3 minutes of deco. That seems like a bad trade off in the risk/reward category. If that is what an agency is teaching, I would really like to hear the logic in how they defend that guidance.

Perhaps they just assume you are really not going to tox out at 130 on 40% for a while, and assume the diver will initiate an immediate ascent?

Quick sim in SubSurface, a 15min deco on 32% became a 13min deco on 40%

 

[CAPTAIN SINBAD]

I agree a lot with this. How much reduction in deco is generated from using a 40% mix versus a 32% in the bailout bottle? Say from a 10 minute deco penalty?

I have no software to answer the question, but I would assume/guess that the rich mix would shave less than 3 minutes of deco. That seems like a bad trade off in the risk/reward category. If that is what an agency is teaching, I would really like to hear the logic in how they defend that guidance.

Perhaps they just assume you are really not going to tox out at 130 on 40% for a while, and assume the diver will initiate an immediate ascent?

Exactly. Back gas decompression is no problem. As a decompression diver, you do not have the option of surfacing in case of any emergency so part of the training is to solve problems without surfacing. In case of twin tanks you shut down a valve or isolate the problem and if you are diving singles then two separate first stages connected to the same tank as redundancy. Neither of these are typical recreational set ups and better wording is needed than "recreational" gear.

 

[inquis]

Neither of these are typical recreational set ups

Deco pony.

 

[CAPTAIN SINBAD]

Deco pony.

As discussed, that would work if it has the same gas as your back gas and allows you the option of switching wherever a catastrophic gas failure happens. If you are carrying a higher nitrox mix for decompression then the MOD of that may not match your back gas. This will prevent you from switching on certain profiles.