Deep Air?

[Basking Ridge Diver]

Your math is correct - 219 feet @1.6 po2.

 

[sheeper]

i follow the rule of never, never, ever, ever use 1.6 (except maybe on a deco stop)

 

[OrangeCountyScuba]

@sheeper
Agreed, however I was using that as an example to open up the discussion about deep air. It kinda plays into the whole conversation, as history has shown certain divers doing deep air tip toe with those rules.
@Basking Ridge Diver
Thanks for confirming.

 

[sheeper]

keep in mind that you can dive deep on air AND use air as a deco gas. it just takes (a lot) longer

 

[OrangeCountyScuba]

@sheeper
Yes I am well aware. The whole reason I started this was earlier in the week I had a student ask me about the book Shadow Divers and he mentioned them diving deep air at one point then switching to Trimix later on. So I was just curious to see if there were people still diving deep air since that was the "thing" to do obviously before the introduction of Trimix.

 

[Peter69_56]

My guess would be that there's a fair few divers who make deep air dives due to the high cost or limited availability of helium. I'd also guess that they'd rather be using trimix, all things being equal.

For a diver to prefer deep air diving..... well, they'd have to be pretty "diehard". They certainly couldn't blame their preference on a lack of available training or education...

Exactly. I would prefer to dive helium on all dives below 45m but given the high cost of helium in some areas of the world, this equates to $1000 a dive. My budget is good, but it doesnt allow for diving at that cost. At home a dive would cost me in the order of $250 a dive for gas, so it would have to be a special dive or a very deep dive to justify the additional cost. Remembering as well as the $250 for the gas, I have $90 for the charter, $50 in fuel costs so in the order of $400-500 a dive. Try doing that on a weekly basis. Now that is no justification to go to say 80m on air just to save money, but I would go to around 60m regularly (depending on conditions and gas volumes etc). I am certified to 55m for air and "to date" have had no issues with regularly diving to that depth on air.

 

[PfcAJ]

Exactly. I would prefer to dive helium on all dives below 45m but given the high cost of helium in some areas of the world, this equates to $1000 a dive. My budget is good, but it doesnt allow for diving at that cost. At home a dive would cost me in the order of $250 a dive for gas, so it would have to be a special dive or a very deep dive to justify the additional cost. Remembering as well as the $250 for the gas, I have $90 for the charter, $50 in fuel costs so in the order of $400-500 a dive. Try doing that on a weekly basis. Now that is no justification to go to say 80m on air just to save money, but I would go to around 60m regularly (depending on conditions and gas volumes etc). I am certified to 55m for air and "to date" have had no issues with regularly diving to that depth on air.

what are you paying for helium?

 

[scubadada]

Uh no, I did mean 1.6 ppO2 at 219 fsw. Unless, the math has changed and I am not aware.
1.6ppO2/.21O2= 7.62ATA-1ATA= 6.62ATAx33= 218.46 fsw, is this math wrong? Someone else want to confirm this for me?

pO2 of 1.4 is the usual limit for working pO2. 1.4/.21 = 6.67 - 1 = 5.67 x 33 = 187 feet, my mistake.

 

[Diver0001]

Referring back to Rob's post this is one of the things I looked at when I became an instructor and realized the deep dive of the AOW or Advanced class for damn near all agencies was approached in the standards and the materials really half-assed. This was based on my now experience with technical diving and how the approach to any dive is so different.

As a result,within the standards of SEI, I wrote my own deep dive standards (in fact the entire Advanced course I offer) that more closely reflected the approach to dives from a tech standpoint. As such I talk a lot about narcosis and the different forms it can take. Also talk a great deal about "managing" it and how those management techniques can be effective for 10, 20, even 30 dives; but let one variable be a little different on that one day and all those techniques go right out the window.

Jim,

I think you and I are on pretty much the same page about this, although we have very different opinions about the standards and how to approach the issue.

The standards for learning to deep dive within many agencies, including technically oriented agencies, take, I believe, an optimistic stance with regard to the skills/experience of students coming into the course. That's where the problem I perceive begins. Standards would appear to set prerequisites based upon optimism instead of realism. That's not a PADI problem, to be clear, that's an industry wide problem. If you look at the prerequisites for some technical classes, it's toe curling how little experience someone needs in order to engage in extended range or deep/Trimix diving.

For recreational diving, PADI attempts to "solve" this by putting the responsibility for judging the student's readiness into the hands of the instructor. Most con-ed courses begin with an "evaluation". That's wise, and a good thing for conscientious instructors, but also a subjective thing that gives crappy instructors WAY too much wiggle-room.

Ideally I like to train for advanced when someone has some experience. Too much isn't good because then they either don't really need it or the "bad habits" are harder to unlearn. Not enough isn't good either because advanced is a course, because of the deep component, that adds a level of risk to the dives that some divers simply aren't ready to handle.

I've just seen too much to think that deep diving should be taken lightly. We still get together every year with the student we rescued from his dive-team a few years ago when the deep dive got totally off the rails. It was an experienced instructor (of the type who looks for the wiggle-room) who had a team of staff who were beyond incompetent..... the blind leading the blind. Yes, for all of the strengths, the system also allows for this kind of thing.

It lead to an accident that by all accounts should have been fatal, had we not been there--completely coincidentally--ready to dive, and intimately familiar with the dive site, to pull that student back through the eye of the needle.

So your reaction to this situation was to write your own standard. My reaction to it is to be very picky about who I train for deep diving. As a PADI instructor I am not *required* to train anyone. I train who I believe is ready for it. Working part time for a shop, of course, there is some pressure to do advanced courses, but I'm very clear that I only want to do OW for them because THAT is where I can set a firm foundation that the student can fall back on. When they want me to do advanced, I do the navigation (which I REALLY like), and other "experience" dives, but I seldom finish advanced because I pretty much refuse to do the deep dive(s) unless I feel, after seeing the student in the water, that the student is prepared for it.

This may seem kind of ironic because if you look at it, from all of the instructors at the shop where I work, I'm the one, by far, with the most deep experience and also the one, by far, who is most reluctant to take a student deep. I think that says something about standards. I guess PADI would say that it says something about me....

R..

 

[DevonDiver]

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