Redundancy Required for Decompression Diving?

[100days-a-year]

Maybe it's the unpasteurized cheese and sulfite free wine that allows them to be so nonchalant,the French do a have a distinctly different approach to many aspects of life.Vive la difference!

 

[Reku]

IMO - if you are doing any kind of diving with either a synthetic ceiling imposed on you by yourself (deco) or a hard ceiling (overhead) you should have redundancy in gas and buoyancy.

However - it is not required and as such you can do whatever you want to do.

 

[hroark2112]

I am absolutely willing to strap on my rebreather and breathe on it with no bailout.

Until it's time to leave the boat. Once I'm wet, I want my bailout!

 

[halocline]

I have not taken any technical dive training, so I am curious about this topic. Recently, a technical instructor has indicated that he was "OK" with exceeding the no-deco limits and continuing a dive causing the accrual of a (moderate) decompression celing without the benefit of redundancy.

Is this consistent with current technical training? Is reliance upon a buddy's gas supply considered sufficient redundancy in this sort of situation? Based on training guidelines, would this be OK with a buddy and maybe not OK while solo diving?

Do the technical dive courses discuss this sort of thing or is it left to the discretion of the instructor or the diver?

I'm not really sure what your motivation for asking this, but I guess my answer would be it doesn't matter what the details of a particular agency's "rules" are in a situation like this. You can be assured that all technical diving agencies will specify that redundancy is required in all overhead diving scenarios, including decompression ceilings. Beyond that, I guess what you do is up to you.

If you are really interested in the details of technical diving, I would suggest you take some classes. That way you'll know exactly what the agencies think.

There is an analogy between 'technical climbing vs hiking' and 'diving that borders on NDL/slight deco requirement'. In both cases, there are some environments or situations that are clearly non technical, some that are clearly technical, and some in that fuzzy area in between. There are places where some climbers are perfectly happy scrambling with no protection, even though a fall could be quite dangerous. Others in the same place would insist on using ropes and a harness. With diving, some divers are happy to incur deco obligations with no redundancy, even though a gas loss could result in DCS, and others won't go near violating NDLs without the protection of a redundant gas source. Complicating this is the fact that some computers will indicate a deco obligation while others on the same dive will not. So who knows exactly when it's safe to surface.

Everyone's risk tolerance is their own. I tend to pad my safety in deep and/or repetitive OW dives by extending my shallow stops, because it's easy and enjoyable, I feel better post-dive, and I have respect for the 'fuzziness' of decompression limits.

 

[boulderjohn]

My question originated because, on another thread, a technical instructor (a SB moderator) seemed to be indicating that he was OK with no redundancy on a deco dive.

I am the person he is referring to, inaccurately. What is his motivation? He loves nothing more than attacking me in threads, and he does so at every opportunity. He needs no other motivation.

The other thread was the lite deco thread. In it, I talked about the fact that I dive a Shearwater Perdix in tech mode while doing recreational dives, and in that mode it runs out of NDL before other computers do, but when it does, it is calling for only a one minute stop. I don't worry about it. I went on to talk about other computers going into deco and really only requiring a safety stop or another minute or two at the safety stop. I said I would not worry about that either. Obviously that includes the realization that I have plenty of gas for that extra minute or two. Even if I didn't, that missing minute or two of deco is not going to matter much at all.

I then went on to say that if I plan decompression or anything more serious than described in the paragraph above, I would definitely want to ensure that I have redundant gas so that I could be sure of doing the required decompression.

So, strictly speaking, I did say it was OK to do some deco without redundancy. If you want to make the OP's day, you should all now pile on me and call me every name in the book. Some of you should report me to my agency. If you would all do that and make me out to be a pure scumbag piece of crap, it will really make his day, and he will sleep well tonight.

 

[sunnyboy]

I am absolutely willing to strap on my rebreather and breathe on it with no bailout.

Until it's time to leave the boat. Once I'm wet, I want my bailout!

Same here!

That's one lovely thing about diving my rebreather - I always have an appropriately sized bailout for the dive I'm doing. If I'm doing a dive that *might* incur some deco, then the bailout will get me home, including that deco. If the dive really isn't going to involve deco (like say 1.5 hours at max 60ft) then a smaller bailout may suffice.

My dives tend to be long but not all that deep. Bailout-wise, I'm usually more worried about a long swim home than actual deco.

 

[boulderjohn]

Here are the posts that led to the creation of this thread:
"Riding your Computer Up" vs. "Lite Deco"

"Riding your Computer Up" vs. "Lite Deco"

"Riding your Computer Up" vs. "Lite Deco"

 

[scubadada]

I am the person he is referring to, inaccurately. What is his motivation? He loves nothing more than attacking me in threads, and he does so at every opportunity. He needs no other motivation....

Hi @boulderjohn

Seems like this topic has gotten a little out of hand. I never thought @dumpsterDiver was leveling personal attacks, but only he can answer for himself.

As a long time light decoer, I was also interested in how the training agencies felt about light deco without redundant gas. The light deco thread got sidetracked all over the place with the discussion of various deco algorithms, liberal and conservative, and what that meant with regard to light deco.

I have a feeling that all training agencies would recommend/require redundant gas for any amount of deco, that's the conservative approach. However, I don't know if that question was ever directly answered. The same thing probably goes for solo diving, to say nothing of solo light deco.

In the end, we all have to accept our own level of risk, regardless of the recommendations or requirements of the agencies. I am very comfortable with the profiles I dive that have remained unchanged for many years. This topic has been quite interesting, I'm glad @lowviz brought it up.

Happy holidays and good diving, Craig

 

[boulderjohn]

I never thought @dumpsterDiver was leveling personal attacks, but only he can answer for himself.

You have to know the years of history behind this. My policy in general is not to read his posts, especially in a thread in which I have participated previously, because there is a good chance it will contain a personal attack that will raise my blood pressure unnecessarily.

 

[sea_otter]

When I am recreational diving, I use a Perdix, and I have never bothered to take it out of tech mode. I don't even know what it looks like in recreational mode. You bet it runs out of NDL well before the others, but if you ascend immediately after going into deco, you will find that when it does, it requires a one minute decompression stop at safety stop depth. Sure, if you stay in deco long enough at depth it will run all the way up to 3 minutes (like everyone else) and even beyond, but when it first goes into deco while in tech mode, it is really at the beginning stages of calling for a real safety stop.

Recently, a technical instructor has indicated that he was "OK" with exceeding the no-deco limits and continuing a dive causing the accrual of a (moderate) decompression celing without the benefit of redundancy.

Uh... yeah. Reading those two side by side, they're definitely not talking about the same thing.

I suppose by these definitions you could argue that the PADI deep diver specialty teaches deco without requiring redundant gas? I have not taken it myself (nor do I plan to), but I believe they introduce the concept of "mandatory safety stops". I'd venture to say that fits John's definition closer than what's being discussed in this thread.

I suppose next time I should go and seek out the real story before replying to a post.