Reconsidering Deep Air?

[Wibble]

Your right, you certainly don't want CO2 hit, but..............by the same token you (the collective you that is) shouln't need other peoples bailout gas or need other people to keep you alive (underwater). That's being reliant. And even if diving with a buddy you (again the collective you that is) want to be totally self reliant and / or simply accept the consequences if your not.

Might be nice to have someone else there when the s@#t hits the proverbial, but then again it might not. Whatever, you shouln't be dependent on them.

Totally agree.

However... When you're diving deep, you cannot take enough gas with you to do the dive with a sensible bottom time and survive a full on CO2 hit -- if you go by their elevated gas usage numbers that the agencies use.

Hence the major difference between MOD2 and MOD3 diving; where MOD3's about team diving more than self-sufficiency. At those depths a CO2 hit is very serious indeed.

 

[Hartattack]

It is always reasonable to ask why you want to go deep on any gas. The answer to risk avoidance is stay shallow rather than use Helium. As most of you know, Helium will help reduce risk but is a long way from eliminating it. (Not everyone reading this thread is a trained technical diver)

There is a long history of working dives on air far deeper than modern training agencies like to admit. However most were accomplished using surface supplied systems and divers with literally months (8 hours/day and 5 days/week) of training and many years of experience. Surface supplied doesn't change the physics or physiology but dramatically changes the risk profile.

For perspective, all US Navy First Class Divers made dry and wet chamber runs to 285'/87M when the PPO2 limit was 2.0 instead of 1.4/1.6.

View attachment 649550​

We were taught techniques to manage CO2, in the body and the gear, which produced nearly immediate results. Narcosis symptoms didn't disappear, but improved quite noticeably by the diver and topside support crews.

The US submarine F-4 sank off Pearl Harbor Hawaii with all hands in 1915. She was in 306'/93M of water. All divers survived though efficiency was severely reduced by Nitrogen Narcosis. The F-4 salvage was the leading motivator to develop HeO2 diving in the 1920 and 30s at the US Navy Experimental Diving Unit.

Obviously, deep air risks can be managed but it comes back to the original question, why are you making the dives? Exploring wrecks in remote locations with minimal facilities might be one reason for deep air. The cost and availability of gas might be another.

In my experience, slowly working deeper in order to learn to manage symptoms is a critical component. There is considerable debate regarding short term diver acclimatization to Narcosis. It may not be measurable by conventional cognitive tests, but higher work efficiency was consistently reflected in diver's performance on all the commercial deep air jobs I have been on.

How do you know a Navy Diver is in the room? They will tell you.

 

[helodriver87]

Doing my first 70+m / 220' dive on open circuit, I was astounded how quickly the back gas was consumed. With those deep dives on OC, it's all about being calm and conserving gas as your bottom time is determined primarily by your minimum pressure and secondarily by your deco plan. In a phrase; be frugal with gas.

With CCR you can pretty much huff and puff as much as you like without consequence - within reason. The planning is all about bailout and how much you overestimate for "Your CO2 Hit", the biggest fear of a CCR diver. The guidelines say you should calculate for a SAC of 45 litres/min (1.6 CF per min), which at depth means you consume absurd amounts of gas
Maffs: 80m/250' = 9 ATA = 45x9 = 405 l/min (1.6CF x 9 = 14.4 CF/min) in other words emptying an ali80 in 5.5 mins -- if you can get on it without drowning.

Hence you a) don't want a CO2 hit, b) need other peoples bailout gas, c) need other people to keep you alive.

d) bailout early

I've been significantly CO2'd on OC before (overexertion, bad technique, and a poorly fitted neck seal) and it's terrifying. Since then, I've come close to doing it again, but I've started recognizing the symptoms. The first one I notice is a feeling of impending doom that I can't tie to a logical thought. That tells me to slow way down and relax. If that doesn't fix it, bailout while your RMV is still manageable.

 

[Atlantic Explorer]

Some people can walk home after 20 pints of beer

They might be able to walk home but are they able to walk in a perfectly straight line?

 

[Couv]

They might be able to walk home but are they able to walk in a perfectly straight line?

I can, but unfortunately only on a winding path.

 

[Centrals]

As as you well know, or should I expect given where you live, the visibility / conditions in some areas of the SCS, Malacca Strait and Java Sea is far far from ideal, especially at 60m. But doable - if experienced - and yes have done it on OC many times too, but only because helium was not available on board for whatever trip that may have been. So not out of choice on my part, just no gas available that time round. So if I didn't have gas and there was a 60m dive to do in open water on a wreck, then not having gas would not stop me from doing the dive, all other things - current, sea state, etc - being equal. But deep air is not something I would recommend to others, although I wouldn't try to stop them doing it either, unless they were complete newbies / unaware of whats 'down there'. For some folks it's a nightmare and then there are others that should never even attempt it, while for a very minority of others - dive boat owners / skippers / skippers 'help' mostly - it's not only almost a daily occurrence, but sometimes a couple of times a day. And that is something I have personally wtnessed many many times.

I have made a few trips on those WWII deep wrecks and others(eg. Seven Skyies) in Asia. Helium was always available and I have no problem to pay for it.
My definition on OW is for reef/wall dive only as vis is never an issue. Wrecks deeper than 50m is different ball game entirely.

 

[Kay Dee]

Totally agree.

Hence the major difference between MOD2 and MOD3 diving; where MOD3's about team diving more than self-sufficiency. At those depths a CO2 hit is very serious indeed.

A very serious business indeed is a CO2 hit!.

But.........although I have done 'team diving' when required on wreck surveys, etc, most of my diving has been photographing wrecks in the - I suppose you might say - 'mid range depths' of 50 to 75m has been solo on CCR, with on occaison a same ocean diver - I certaily couldnt call him a 'buddy' - on the wreck at the same time. But where on the wreck, well I didnt have clue and could have cared less.

 

[Kay Dee]

I have made a few trips on those WWII deep wrecks and others(eg. Seven Skyies) in Asia. Helium was always available and I have no problem to pay for it.
My definition on OW is for reef/wall dive only as vis is never an issue. Wrecks deeper than 50m is different ball game entirely.

Argh yes, a 60m dive in warm clear tropical water, say in the Phils, GBR or Cozumel maybe, on a reef or wall is a whole other ball game than say a even a 30m dive in the Baltic for instance, where it's might be plus 2C / 3C on the bottom, and as dark as a unlight coal mine, although vis can still be very good, as long as you have a powerful enough light. IMO it's all, or mostly, about experience and conditions, is depth sayeth Yoda. Oh, and gas density, should you care to factor that into the equation.

As for those Asian wrecks - which unfortunately are mostly all gone save for HMS's Repulse and PoW, and I assume USS Lagato, and even those first two shadows of their former selves courtesy of illegal Chinese salvors - you may even have gone out on the same boat of which I speak (Empress) regarding a certain owner / skipper's predilection for deep air diving.

 

[Pressurehead]

How do you know a Navy Diver is in the room? They will tell you.

You made that up, did you not, from some other quote?
Most [if not all] 'Navy Divers' I know say "diddly-squat" in an room, especially if the Conversation is around "diving", could not give [a rats] or care what civilian divers think or say or do.
I found the more civilian recreational divers [so called pros] I met and dived with, the more I liked my neighbor's cats, and I don't like cats.
Never said a thing then, too old now and the "fire wall" in the brain has broken down, and still do not like [let us say] cats.
I am mellow now, just blurt it out.
Rant over.
B.Z. Divers.

 

[Centrals]

As for those Asian wrecks - which unfortunately are mostly all gone save for HMS's Repulse and PoW, and I assume USS Lagato, and even those first two shadows of their former selves courtesy of illegal Chinese salvors - you may even have gone out on the same boat of which I speak (Empress) regarding a certain owner / skipper's predilection for deep air diving.

I really wished I had made that trip to dive HMS Exeter unfortunately I had other engagement. Apparently the whole wreck has gone!!!!


Retired to Lombok few yrs ago and sold the boat to Froggy divers.

Raja Ampat