What is "Deco" training?

[Ben]

I've never heard of Rec 3. It sounds to me like Rec3 was the course you may have wanted to skip and why there are potential issues with a tech 1 course. Clearly you have progressed to what the agencies have decided is a technical level (overhead diving and/or exceeding NDLs).

[LCF]

Rec 3 is a class aimed at training the recreational diver for the 100 - 130 foot range, and to use a low percentage of helium to reduce narcosis. It may be unique to Breakthru Diving at present, although it's quite similar to GUE's Rec Triox class. Most people who have taken the class have done so in doubles. Skills included managing valve failures, OOA scenarios, mask loss, SMB deployment and failures, etc.

Richard, are you referring to the O2 window?

[KMD]

One thing that was stressed heavily after tech 1 was that:

"You are responsible for your own deco."

Screw it up and you have nobody to blame but yourself.

The only thing I would like someone to have is the knowledge and skills to realistically look at the risks of doing a dive and be able to mitigate them as needed.

Whether that experience comes through training, mentorship, experience, or the school of hard knocks just so long as its there is the main importance.

I myself would recomend having at least two of the first three before attempting to push one's limits.

[rjack]

There's the mysterious "o2 window" which I believe exists but to a lessor degree than its hyped up to be. There is also the ability to crush bubbles and remove them by having a tissue bubble to dissolved blood gradient gas gradient. Which is a varient on the blood to lung gas gradient through reduction of the inert fraction you are attempting to eliminate. And lastly there's pressure gradient reductions. So a deco gas (chosen appropriately) gives you 3 offgassing modes while backgas gives you one.

Really, deco on backgas is not ideal. Nobody teaches just backgas deco because if you have an overhead obligation you deserve the proper tools to manage it. You can chose to take those tools or do the deco on backgas. E.g. I will deco on backgas occasionally because its simpler. I think I've done that twice in the past 3 yrs.

But really you guys just finished a recreational MDL level trimix class which had a tiny amount of contingency deco discussed. You have what 2x 25/25 dives to date?? Now here we are talking about how far you can push it. How about y'all get 30-40 dives conservatively using your current toolset and then you won't have to ask on the internet if XYZmins of deco is ok or foolish. You'll have a basis of experience to make you own judgments on whether to do the dive, skip the dive, or take the next level class.

[Ben]

Rec 3 is a class aimed at training the recreational diver for the 100 - 130 foot range, and to use a low percentage of helium to reduce narcosis. It may be unique to Breakthru Diving at present, although it's quite similar to GUE's Rec Triox class. Most people who have taken the class have done so in doubles. Skills included managing valve failures, OOA scenarios, mask loss, SMB deployment and failures, etc.

I checked out the website and I now understand the issue. All of these new rec classes that have somewhat blurred the lines between rec and tech. You have done the extra courses but on the wrong path (tech vs rec). There's not a great answer other than the agencies have picked the most clear delineation possible. Rec is no deco and tech has deco.

I'm not sure if the original question was more based on pushing the limits in cave, your local open water dives, or just for general information and not yourself personally. What does an extra couple minutes of bottom time gain you?

If this is about you specifically, I think you took the wrong courses. Even if you think differently you are doing (cave) and are asking to do (deco) tech dives.

[LCF]

I don't know why I keep coming back to this, because it isn't my thread. I'm the person who won't break 6ths by 50 psi!

Richard, there's no question that accelerated deco is more efficient. But you CAN deco adequately on backgas. It's just slow. It's not optimal, but the differences become much more marked as the deco obligation increases.

Honestly, my midwater skills aren't deco ready, but my intellectual understanding of the topic probably is!

Anyway, Ben, just to clarify, Peter and I have both done a proper cave class, cavern and Intro. So we're not cave diving on rec certs, if that's what was bothering you. And we're not doing deco in caves (or anywhere else) at present. But these "techreational" classes do begin the blur the line a little, I think.

[Ben]

I don't know why I keep coming back to this, because it isn't my thread. I'm the person who won't break 6ths by 50 psi!

Anyway, Ben, just to clarify, Peter and I have both done a proper cave class, cavern and Intro. So we're not cave diving on rec certs, if that's what was bothering you. And we're not doing deco in caves (or anywhere else) at present. But these "techreational" classes do begin the blur the line a little, I think.

No, your caving was not bothing me, but I think all cave divers (at least in FL caves) should be deco trained to begin. I can rack up considerable deco time on my backgas even if I limited myself to 1/6s. The particular problem is you've done 90% of the work but because the class was labeled "rec" you have a limitation imposed. Can't do much about it now, but the advanced "rec" course are pretty useless for anyone that has tec aspirations. Not because the course is not good, but you have to take other courses "over again". I would ask your instructor if he would consider a mini course to fill the minor gaps in training with your unique desires in mind (limited and back gas deco only).

With that said, I think you will want a deco bottle in FL eventually......

[ae3753]

What's wrong with repeating a portion of a class and getting re-evaluated? The next time, you'll have more experience (presumably be a better diver) and able to push yourself to another level?

[rjack]

Richard, there's no question that accelerated deco is more efficient. But you CAN deco adequately on backgas. It's just slow. It's not optimal, but the differences become much more marked as the deco obligation increases.

No its not just a question of speed. Its a question of whether you think that offgassing using only a pressure gradient reduction is appropriate. Sometimes it is, sometimes it isn't. AG called a Buhlmann 30/85 shape on backgas "ugly deco" in my class. That's why its generally me and my buddy's contingency, not our primary plan.

For the upcoming dive Sunday, DIE and I are using 25/25 and O2 deco. Even though we will probably only have a 10-15min obligation, the O2 is not only faster its a cleaner deco because it can force bubbles to shrink. A backgas curve won't do that.

[gcbryan]

On another thread relating to Ratio Deco (RD), I made the comment that I thought RD gave me a tool for what I called "tweener" dives. In context I believe the notion of a "tweener" dive was one that was in "recreational limits" but pushed, or slightly exceeded, the "NDL's" and so some extended decompression was desirable.

This led to some comments that can be summed up as "If you haven't taken Tech 1 (or its equiv) you shouldn't do extended deco dives." (Extended deco being defined as anything more than minimum deco per GUE/Breakthru Diving.)

This has led to a household discussion on the topic of "Why?" Why should a "techreational" diver be limited to minimum deco dives if he has had the training of:

1. Ratio Deco (giving a tool for defining an appropriate deco strategy for any particular dive);

2. Safely diving a square profile with overhead limitations (in this case Breakthru's Rec 2 and Rec 3); but

3. No experience (nor desire) to use a "deco" gas.

In other words, what training does one need for doing Back Gas Deco other than:

1. Gas planning (to identify how much gas one needs for various contingencies);

2. Ratio Deco (to create an appropriate ascent/deco profile on the fly);

3. Failures training (managing failures appropriately)?

Is there not a place for "tweener" dives for people like me to do some extended deco without having to "play with" bringing extra bottles?

Litterally the answer is that on the one hand you can do anything you would like to and on the other hand no certification is going to "allow" you to do something for which you haven't been trained.

I'm not sure of the exact point of your question but are you asking/wondering if there is a deco course out there for non-tech divers which doesn't involve deco gasses? I'm sure you know that the answer there is no.

Are you wondering why an agency doesn't santion extended backgas deco with no deco gases? That wouldn't make sense either.

If you are asking what's the problem with exceeding air/nitrox NDL's in the 100-130 fsw range by no more than 5 minutes. To me there is no problem doing that but it doesn't buy you a whole lot of time and doesn't really require an additional class to do just that. Double your minimum deco schedule and it will pretty much take care of that scenario.

[ae3753]

But these "techreational" classes do begin the blur the line a little, I think.

I think that diving MDL and more specifically Peter's DIR-Diver.com MDL table already blurs that line.

[LCF]

I'm going to wait and do my deco training in Cave 2. I think I've had all the midwater harassment I have the stomach for for a while.

[Peter Guy]

To go back to the original question -- What is "Deco" training? I happen to think it is a pretty simple question -- apparently some respondents aren't so sure.

I suppose another way of asking it is: In order to do a "Deco" dive, must (or should) one always use a 2nd (or more) gas? At least one respondent seems to be pretty clear that one should never plan a deco dive to use only backgas deco. And since using an additional gas means an additional bottle (which means additional skills) that means an additional "class."

So, I guess another way of asking the question is:

What are the skills and cognitive information necessary for the safe planning and execution of a deco dive? Is it your belief the skills and information are only available from a "Tech 1" (advanced nitrox) type class?

[KMD]

To go back to the original question -- What is "Deco" training? I happen to think it is a pretty simple question -- apparently some respondents aren't so sure.

I suppose another way of asking it is: In order to do a "Deco" dive, must (or should) one always use a 2nd (or more) gas? At least one respondent seems to be pretty clear that one should never plan a deco dive to use only backgas deco. And since using an additional gas means an additional bottle (which means additional skills) that means an additional "class."

So, I guess another way of asking the question is:

What are the skills and cognitive information necessary for the safe planning and execution of a deco dive? Is it your belief the skills and information are only available from a "Tech 1" (advanced nitrox) type class?

All dives are deco dives. Some require more deco than others. There is no black and white answer on what is needed. Deco is not an exact science so we shouldn't really assume skills are exact either. We can look at the wide range of levels instrutors teach to as proof of this.

We can see some general trends though. Consider the case of blown deco:

100' for 20 minutes - good chance of walking away with little to no effect
150' for 20 minutes - high potential for type 1 hit. Chamber or O2 may fix/prevent hit.
240' for 20 minutes - high potential for type 2 hit. Chamber probably required. potential long term nerve damage.
300' for 20 minutes - high potential of death.

These are meant to be very general statements that show the trend that as we go deeper, the risk level goes up and thus ones skills, training, and experience must also be higher.

Training doesnt prepare one to dive at any of these levels. It only gives a framework which the diver has to fill in with his/her own experience.

[LCF]

Very good post, Kevin. Puts things in perspective.