BackMounted Doubles and mixed gas - is that technical?

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Basking Ridge Diver

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So I planned my dive on the Stolt Dagali of the NJ Coast. Sand is about 125 feet and the wreck goes up to about 70 feet.

I used Subsurface software which I have used before and calculated my dive times and gas usage. I was going to just use air for the entire dive but realized my second dive would be cut short due to my Nitrogen load (NDL driven - I am not AN/DP certified) - but I do have my Nitrox certification.

I dive Independent doubles and used air in one tank with the long hose and used 40% in the other under my chin. 40% at 82 feet is 1.4 PPO at 100 feet it would be 1.6 PPO- my plan was only to use it after I get to 80 feet and use half the tank. Saving the other half for the second dive.

I got some questions from fellow divers as to what I was doing and someone mentioned the fact that you are switching gases makes this a technical dive. To be fair I never really thought about it. I used air to get to the deep stuff and used 40% which I am allowed / certified to use and extended my dive due to the nitrox - getting me the longer NDL on both the first and second dives.

I happen to have a Perdix so I marked 21% and 40% did the gas switches and just followed my NDLs. No harm no foul. I did not go into deco and no one was checking my dives - I dove solo but went down the line with a "Buddy" because he wanted to make sure he was ok - I had no problem with the arrangement.

I brought 3 tanks - two filled with air and one filled with 40%. Other than OxTox if I made some kind of stupid mistake - it seemed to work for me and my diving style.

Would you consider this a technical dive? I am not a qualified technical diver and I am using the tools that are available to me - it did not seem to me like I was breaking any rules and the dive boat had no issues but I did not announce what I was doing either.
 
BTDT

"Technical" is just a label. No agreement possible on your current transitional status. Suggestion: Take AN as a course by itself. That 'card' has serious value.

Then, take DP. Just get AN squared away first. It is important.
 
The 'technical' diving definition is a complex debated topic.

If the dive is within your skillset, training and you have sufficient experience to safely execute it as planned you're good to go in my books.

I think most people would consider it a technical dive due to the added complexity of a gas switch and carrying deco gas that would be risky to breathe at the maximum depth (exceeding MOD if you grab the wrong reg is not traditional a risk in recreational diving).

Enjoy,
Cameron
 
+1 for what @lowviz said. "Technical" is indeed just a term and lots of folks probably have different ideas about what it means. But, using doubles and switching gases indeed falls within the realm of what many consider to be a tech dive.

Here's a couple of issues with your dive that I see. First, I would never use a gas in my back mounted doubles (independent or manifold) that I could not breathe on the bottom. Your doubles should not only extended your gas supply on the bottom, but also provide a means of bailout in an emergency. Your regulator on a bungee should be available to breathe on the bottom.

Let me give you one example on the dive you did. You're cruising along enjoying your dive on the bottom and suddenly an OOG diver appears and snatches your reg out of your mouth. Now you have two choices, either fight the OOG diver and recover your regulator and leave him to likely drown, or pick up your necklace reg and start breathing 40%. If you pick up your necklaced reg, you are breathing a PO2 of about 1.9. Maybe you'd be OK, maybe not. I sure wouldn't chance it. Alternatively, if something goes sideways, let's say an entanglement, and you breathe your first tank down, your options for switching to your back up reg is not good.

A much better option is to dive both back mounts with your bottom gas. Then sling a 40 cf bottle of a higher nitrox mix for deco. You then train to know that the 40 on your side is for deco only, your other two regs are safe to breathe on the bottom.

Seriously, take an AN/DP course. That set of courses is aimed squarely at the type of diving you are trying to do here.
 
Leading cause of death in tech diving is gas switching to an unbreathable gas. This is among people trained to be very careful about switches etc.

I don't really know when an NDL dive becomes "technical" but having an unbreathable gas on your person puts it over that line for me.
 
Dive to 150 feet with backmounted doubles with 18/45. Technical or not technical?
 
There is no specific card for "technical diving." There is AN, there is DP, etc. From what I understand, gas switching is one aspect of technical diving--that is, one of several--and it can present serious risks to the untrained diver. I would say get some training or mentoring in the gas switching. Of course, if you sign up for a class to do that, your choices are limited to something like DP, which teaches more than just gas switching. You can label your style of diving whatever you like--that's not what matters.
 
Given that you have software available to you and you know how to use it I would suggest that you use that tool to run difference scenarios for your dive day. For instance, I would have probably done the dive with 32% which has a MOD ~111 feet using a working PPO of 1.4. I did some quick runs and could have done the dive twice without any worries while still having the same back gas in both cylinders. Easy peasy and follows the KISS principle.
 
I see 2 questions implicitly weaved into this discussion:

1) What is the consequence of calling something "technical"? An acknowledgement of significantly increased risk? A requirement to obtain training X? If calling something does not have any concrete consequences, it's not very meaningful and we can call it whatever we like.

2) What are the general "design" principles assumed in coming up with this classification? For example, should it be true that if someone is carrying "technical" equipment X or resorting to technique "Y", but could ditch X or abstain from Y at any time and be able to safely complete the remainder the dive as fully recreational, should that make the entire dive recreational to begin with? If not, what are the X's and Y's that make a dive technical, and why? From what other general principle should that follow?

AFAIU, the OP wasn't planning to dive to the bottom, so 40% wasn't unbreathable. Conversely, if we should always consider the possibility of being deeper than planned and use the bottom as a determinant regardless of the planned depth, then what about wall dives with bottom at 200+ ft, should they all be technical?

I have an example of my own. I was several times in a situation, where I dove with someone, who likes to dive with less conservative GF. I would dive with an O2 bottle and have a short deco, whereas the other person would complete the dive with just barely an extended safety stop. I would occasionally get comments that my computer is "broken" or that the deco obligation "wasn't real" (the wisdom of such comments is a whole separate discussion). Were those dives recreational or should they be considered technical? On one hand, I was carrying dangerous gas and using "techniques" (like plugging a different regulator in my mouth) that go outside the scope of what's taught in most rec courses. On the other hand, there is a valid perspective, from which neither was strictly necessary. Which perspective should be applied and why?
 
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