What is SSI's "Decompression Diver" course?

[L13]

Not sure I would agree with this. Physiologically, yes, they are the same process (regardless of gas being used - which just accelerates the physiological process), but in terms of the parameters of the process - vastly different. By definition, a recreational diver completing an optional (but recommended) safety stop has on-gassed Nitrogen below the "threshold" that would make a direct ascent to the surface a reasonably low risk, while a diver that has entered deco has crossed that "threshold" and now has a more elevated risk of decompression sickness should the diver ascend without a stop, and that risk goes up the further over that "threshold" they crossed. I put "threshold" in quotes because we all know that it is not some thin line of precise demarcation, but rather a zone between mostly safe and definitely bent.

Doing a safety stop is essentially saying the "threshold" isn't safe enough, lets set a new threshold a requiring a 3min stop but give it a new name and call it optional so we can say it isn't the same even though, as you admit, it is physiologically the same.

 

[scubadada]

Except for "managing their gas" recreational divers have been doing decompression stops for years. They just don't realize it. They're called safety stops. Physiologically, there's no difference between a mandatory deco stop and a voluntary safety stop. They both off gas the critical tissue(s) to a safer level before ascending. The difference could be in the gas used to decompress and/or the precision of maintaining the stop (technical vs. recreational). While the original idea of the safety stop was to provide additional safety, it can also be viewed as a nudge toward the skill needed to hold deco stops for more demanding technical diving.

Not sure I would agree with this. Physiologically, yes, they are the same process (regardless of gas being used - which just accelerates the physiological process), but in terms of the parameters of the process - vastly different. By definition, a recreational diver completing an optional (but recommended) safety stop has on-gassed Nitrogen below the "threshold" that would make a direct ascent to the surface a reasonably low risk, while a diver that has entered deco has crossed that "threshold" and now has a more elevated risk of decompression sickness should the diver ascend without a stop, and that risk goes up the further over that "threshold" they crossed. I put "threshold" in quotes because we all know that it is not some thin line of precise demarcation, but rather a zone between mostly safe and definitely bent.

Doing a safety stop is essentially saying the "threshold" isn't safe enough, lets set a new threshold a requiring a 3min stop but give it a new name and call it optional so we can say it isn't the same even though, as you admit, it is physiologically the same.

We recently had this discussion in great detail, let's not do it again, OK? There are at least 2 camps that will never agree.

 

[L13]

We recently had this discussion in great detail, let's not do it again, OK? There are at least 2 camps that will never agree.

Ok!

 

[Angelo Farina]

Not sure I would agree with this. Physiologically, yes, they are the same process (regardless of gas being used - which just accelerates the physiological process), but in terms of the parameters of the process - vastly different. By definition, a recreational diver completing an optional (but recommended) safety stop has on-gassed Nitrogen below the "threshold" that would make a direct ascent to the surface a reasonably low risk, while a diver that has entered deco has crossed that "threshold" and now has a more elevated risk of decompression sickness should the diver ascend without a stop, and that risk goes up the further over that "threshold" they crossed. I put "threshold" in quotes because we all know that it is not some thin line of precise demarcation, but rather a zone between mostly safe and definitely bent.

The concept of threshold suggest an hard transition, a sharp boundary between "mandatory stop" and "free ascent".
Instead it is just matter of a continuous function of probability of getting some form of DCS of some degree.
There is no sharp limit.
I always taught my students that "every dive is a deco dive", that a good diver always plans and is equipped and trained for a dive with mandatory deco.

 

[L13]

The concept of threshold suggest an hard transition, a sharp boundary between "mandatory stop" and "free ascent".
Instead it is just matter of a continuous function of probability of getting some form of DCS of some degree.
There is no sharp limit.
I always taught my students that "every dive is a deco dive", that a good diver always plans and is equipped and trained for a dive with mandatory deco.

Quit tempting me! I promised @scubadada not to go there .

 

[gbirch]

Quit tempting me! I promised @scubadada not to go there .

Also holding back, and resisting the

 

[Stoo]

Except for "managing their gas" recreational divers have been doing decompression stops for years. They just don't realize it. They're called safety stops. Physiologically, there's no difference between a mandatory deco stop and a voluntary safety stop. They both off gas the critical tissue(s) to a safer level before ascending. The difference could be in the gas used to decompress and/or the precision of maintaining the stop (technical vs. recreational). While the original idea of the safety stop was to provide additional safety, it can also be viewed as a nudge toward the skill needed to hold deco stops for more demanding technical diving.

Mmmm... not sure I agree entirely, although conceptually I do. The difference between a safety stop and a decompression stop is that if you screw up a safety stop, you "probably" won't get bent. If you screw up a decompression stop you "probably" will.
The addition of a dedicated gas for decompression isn't what defines a decompression stop. Lots of my dives aren't deco dives, but I might just use 02 for my safety stop. Why? Because I can! I'm getting old, and most of my joints hurt most of the time, so I figure adding a little O2 for four or five minutes isn't going to do me any harm. On the other hand, when I'm away somewhere tropical, I may still rack up a decompression obligation and I'm going to do that deco on the same gas I used throughout the dive,

Now before someone unloads about my dive "plan" and it sounding like my deco or safety stops are somewhat "flexible, well you're right. Lots of dives I do consist of something like "swim around looking at stuff until I get bored/cold/low on gas at which point I start up. My computers may or may not be telling me I need to decompress "actually" or not, and I adjust my ascent accordingly. Most of the time, I carry O2, and I always have buckets of backgas, even when I'm "low"...

 

[Blackcrusader]

Mmmm... not sure I agree entirely, although conceptually I do. The difference between a safety stop and a decompression stop is that if you screw up a safety stop, you "probably" won't get bent. If you screw up a decompression stop you "probably" will.

Depends on depth and time. I did my BSAC sports diving courses in the 80's. I was in a BSAC Club doing regular training for a couple of years. Deco dives were the normal dive plans. Not all dives were. This is before people had DC's and nitrox.

Now can I plan a dive with a buddy on Nitrox 32% to 30 metres and factor in 10 minutes of deco time allow for my deco stop and still do that on a single AL 100 tank. Yes. Do I need to have a blackplate wing and long hose setup? No.

 

[Fishdip]

I know you can do tec PADI tec 40 in normal rec gear

All of it raises a lot of questions. Imagine that you are diving to a depth of 130 feet (which is the max depth for this course) and you have a failed valve. If you were in twin tanks, you would shut down the valve and switch to the other tank but here you can not do that because you just have one! You could have switched to your bottle, but that does not have your back gas for that depth but a nitrox mix. so you are below your MOD to make that switch without killing yourself.

Do you hold your breath and swim to the gas switch depth?

How exactly does this course teach you to address that particular scenario, which is repeatedly drilled over and over again in an Intro to Tech? You could ask your buddy for air share, but that fellow is in recreational configuration, which is optimized to take an out of air diver all the way up to the surface. Not a good thing if you both have accumulated decompression obligation which is the sole purpose of this course. Tech divers are trained to do horizontal ascents to the gas switch depth and long hose also enables them to do a stop while air-sharing. Not here.

I am not saying that SSI does not have any solutions to those. If it does start to acknowledge those scenarios, then the course would look exactly like TDI Intro to Tech. Can the jacket style BCD kill you? Yes of course and that is the reason why it is not in popular use when it comes to tech diving. Holding a 20 ft stop, or a stop at any other depth, perfectly still in horizontal trim, without depth fluctuations is a skill that entry level tech divers always struggle with. It is like tight rope walking, where if you inhale just a tad too much, you go up and you exhale a tad too much you sink. Now do a gas switch while holding that depth with precision and it is no longer easy. Most people will be all over the place when they are even slightly task loaded.

As you throw situations such as valve shutdown, deco bottle passing or air share, then holding that depth with zeroed in precision becomes even more difficult depending on the nature of the task. And keep in mind that these are divers who are ideally configured to hold that stop, while being task loaded and they have been repeatedly drilling such things with hours and hours of repetitions.

Anyone who says that they can take a recreational diver, and make them do all of that in a jacket is not being honest to their own self here. But once again, I may be talking totally in the air because I do not know what they are teaching in that course. Still don't. The described parameters of that course raise a lot of questions.

PADI has the same requirements for tec 40. With the cert you are only able to rack up 10min of deco max so the odds of it ending bad are slim if you had to end the dive and do a slow swim up as you share air "if you follow all the required tec procedures. Out of the 25ish single tank dives I have done by the time I hit NDL and start racking up deco I usually hit my 3rd and need to start moving up any ways. Now with that said I do keep a AL-40 21% on me at all times as a backup more so since all of my dives are solo. with that said I do feel safer when using Sidemount but and I am able to spend 30-40min at 10-20 feet doing longer simulated deco and working on skills. So I can understand how you feel about the safety factor, but it really is not that un-safe "once more if you follow the tec rules. Also the last part is a instructor issue because with time and practice anyone can hold perfect trim and do mask and gas drills in a jacket BCD its a question if the instructor works with them tell they can do it or not.

 

[passeparici]

Clubs I know and was associated with, only few designated people can fill tanks and only during designate days of the week.



Yes, almost a year to finish because the "volunteer" instructors have to get on with their busy lives and earn a living and the students gets passed from one instructor to another based on availability.

At the end, the club model may work for some people but it will be a declining number of people. This appears to be the reality of how it is today.

No it is not ! That's your reality because you had a bad experience with this system and you don't like it. It is difficult to speak for the whole world as you and I don't know everything but I can assure you the club model works very well in France for instance. There are more clubs in France than commercial school. They answer 2 different needs and each has ist advantages and disadvantages. Here thousands of divers get certified with a very good teaching. They get a CMAS card (the same with many commercial schools and there is no way someone can print a false CMAS card as they are quite elaborate. I don't know where you live but it is this place that sucks, not CMAS !). I started in a club and I am still in this club. I can go in a commercial place to fulfill some of my needs sometime but I like the way a club works. I now give it some of my time we are quite a lot to do that. Works well...