How deep can tech divers go?

[fookisan]

Saw Deep Sea Detectives and they were diving a wreck at 240. What is the limit for tech diving with air, nitrox or a rebreather?

Thanks,

Dan

 

[Rescue Diver68]

CHatterton was diving a rebreather.

The other guy was using Trimix.

Hopefully some will reply with limits.

I did read where Chatterton has done rebreather dives in the 500ft range.

 

[Rick Murchison]

Saw Deep Sea Detectives and they were diving a wreck at 240. What is the limit for tech diving with air, nitrox or a rebreather?

Thanks,

Dan

Depends...
Air:
From just an oxygen toxicity viewpoint, the current recreational recommended maximum exposure of 1.4 ATA oxygen is reached at 187', and the older 1.6 ATA limit is reached at 218'. (Sea water)
Based on Nitrogen exposure, most tech divers these days recommend not using air below anywhere from 100 to 185 feet, depending on who you talk to.
Nitrox:
Nitrox is more restrictive on depth than air. For example, you reach 1.4 ATA oxygen partial pressure at 111' on EAN32.
Rebreather:
Depends on so many variables - and on the type rebreather used - that a short answer has to be "somewhere between 20 (for an oxygen rebreather) and 450' (for a CCR with constant PPO2 capability) or deeper."
Rick

 

[Hoosier]

The world record is 318.25 m by usng Trimix gas. It required 12 hrs decompression time to the surface.

Check out this site.
http://capeargus.co.za/index.php?fSectionId=342&fArticleId=2557670

 

[oceancrest67]

How deep can technical divers go? It depends on the gas blending, the dive plan and staged decompression.

For regular air: 21% Oxygen is toxic at about 218 feet...also, 79% Nitrogen becomes an increasing threat at depth...tissue loading etc.

I saw the same Deep Sea Detectives. One was diving an Inspiration Rebreather and the other was diving open circuit with a trimix blend (oxygen, nitrogen and helium). From 240 feet you can be sure their staged decompression clocked time.

I believe the world record for open circuit is around 500 feet. I could be wrong.

Just my 02.

 

[MikeC]

Well, how much money do you have? Money for gear. Money for the support divers. Money for all the training you and the support dives need.

Deep air is foolish. People get "narced" on air in as little as 60-80 feet. O2 toxicity is an issue at around 189 feet. The deepest air dive I have read about was around 400 feet and that was not smart.

Nitrox is a shallow water gas. Depending on the mix, less then 110 feet or so.

With a rebreather, don't not. Not trained/certified on them.

If you wish to go deep, you need Trimix. The record is around 1,000 feet. Warning: That is not a "hey, let's go and do a deep dive" dive. It requires months of planning and lots of people and training and MONEY.

 

[Soggy]

So far, the deepest Open Circuit SCUBA dive has been down to ~1000 fsw. Nuno Gomes just recently extended the world record to 1044 fsw. This was a bounce dive, with only a minute or two at depth. Primarily, the limits are a function of amount of gas and time that is required to decompress from such deep dives. Actual sightseeing dives have been conducted to the Edmund Fitzgerald (> 500 ffw) and long penetration dives have been done on the Britannic (400 fsw) with hours of decompression. Some members of this board did a dive to the USS Virginia off of Hatteras in 390 fsw.

Saturation divers can live at depths twice as deep as that. They use even more exotic gas mixtures, sometimes employing neon and even hydrogen.

Eventually, there are physiological limits, but the practical limits of diving on SCUBA are reached long before then.

Note, all of these are TRIMIX dives. Nitrox is a shallow water gas due to oxygen toxicity concerns and air (IMO) is an even shallower water gas due to narcotic concerns.

 

[Rick Murchison]

I believe the world record for open circuit is around 500 feet. I could be wrong.

The air record is about that... Recreational trimix OC record is over 1000', and commercial/military saturation guys have made even deeper.
But back to the original poster's question... and what I think is what he's really after - dives in the 240' range on trimix are pretty common in the tech deep diving arena. As you dive deeper than that, the equipment, cost and support required to safely conduct such dives starts ramping up very steeply... to say nothing of the training and experience required.
Rick

 

[Doc Intrepid]

Saw Deep Sea Detectives and they were diving a wreck at 240. What is the limit for tech diving with air, nitrox or a rebreather?

Thanks,

Dan

Dan, much of what you're asking depends on the context of your question. In other words, define "limit".

Example: open circuit scuba has been used to depths in excess of 1000' by a very few divers. Citation:
http://www.apeks.co.uk/home_frameset.htm
Click on 'Testimonial'.

If you read the accounts, however, these divers used multiples sets of doubles, staged gas, significant numbers of support divers, and weighted lines to which they clipped or unclipped pins to indicate their deepest depth. These were record attempts, and not routine dives.

In actual wreck diving, Terrence Tysall used open-circuit scuba to descend to the wreck of the Edmund Fitzgerald, at 540'. While this wasn't a "record attempt" in the same sense, it was nevertheless a "non-routine" dive for open circuit scuba. They also had staged deco gas and support divers.
http://cambrianfoundation.org/projects/show_entry.php?projectName=The+Edmund+Fitzgerald

While obviously feasible, such dives require substantial logistical support and I suspect are rarely attempted by divers using open circuit scuba. The waste of gas, the number of tanks required, and the logistics burden simply make such efforts increasingly illogical.

While I have no empirical data on which to base my conclusion, I suspect that in terms of routine, frequent, trimix-based open-circuit scuba diving in the open ocean (as opposed to caves, which are a much less dynamic, more static environment), the limits as to what constitutes "achievable" for most teams on open-circuit scuba would be wrecks lying between 200' and 400'.

Rebreathers are an entirely different matter. I'm not qualified to speak to them, however, I'm aware that many rebreather divers are able to descend to depths beyond 400' on a more "routine" basis, because the logistics - in terms of simply providing gas, among other requirements - are less demanding.

There are many other parameters that impact what depth limits are possible, however. One is that weather conditions at sea can change dramatically, very rapidly, so on very deep dives there is always a risk that the weather could worsen while decompression is still ongoing. Caves, of course, being less impacted by weather, are an entirely different matter. Boesmansgat cave drops to 271 meters, and rebreather divers have been to the bottom of it in teams, however, it has claimed more than one life. Nevertheless, deco in caves is not as impacted by changes in environmental conditions as deco in open ocean.
http://www.cdnn.info/news/industry/i050613.html

hope this helps.

Doc

 

[Soggy]

Hey Doc, I beat you to the links Nah nah nah nah nah nah