How deep can u go?

[String]

There also becomes a point where a submarine is cheaper than all the gear needed to scuba it

 

[voop]

12% might keep you alive if you were asleep, but an active diver needs at least 16% O2... and you'll get exhausted quickly if you exert yourself at that level.

Well.....it's the partial preasure of O2, not the percentage of O2, which determines a gas' ability to sustain human life. Very hypoxic mixes may not sustain life on the surface, but they may do so quite well at depth. Hence, for some types of technical dives, a travel-gas is used on decent, until a depth is reached where the hypoxic mix can be used -- i.e. until a depth is reached where the PPO2 of the hypoxic mix is above the limit for sustaining life.

I'm being intentionally vague, since all this is covered in depth in various mixed-gas training -- which is highly reccomended prior to venturing into such diving....

 

[DeepSeaDan]

They "hit the wall" , hyperbarically speaking, during deep diving gas mix research @ Duke University back in the early to mid 80's.

The main problem, if I remember correctly, was in finding additional inert gas combinations to buffer the narcotic effects of helium around the 1800' level ( though 6 times lighter than air, helium's density became problematic around 1800', just as nitrogen does @ the shallower depths we are more familiar with ). Other physiological problems with compression rates in the diving bell at these depths included hpns ( "helium tremors" ).

They nursed a usable mixture of some 4 or 5 gases down to almost 2100' & stopped. This was at a time when deep oilfield diving operations were turning more & more to remotely operated vehicles to do many of the tasks traditionally performed by divers. I guess the commercial-industrial diving complex saw no financial gain ( & great risk ) in continuing to push manned diving limits ever further, so research was effectively curtailed.

Hope this sheds some light.

Regards,
D.S.D.

 

[matt_unique]

Well.....it's the partial preasure of O2, not the percentage of O2, which determines a gas' ability to sustain human life. Very hypoxic mixes may not sustain life on the surface, but they may do so quite well at depth. Hence, for some types of technical dives, a travel-gas is used on decent, until a depth is reached where the hypoxic mix can be used -- i.e. until a depth is reached where the PPO2 of the hypoxic mix is above the limit for sustaining life.

I'm being intentionally vague, since all this is covered in depth in various mixed-gas training -- which is highly reccomended prior to venturing into such diving....

Good point - got to consider the pp02 as well as the % to sustain life. I'm sure more of this will be learned from trimix certification. (Which I have not done yet).

--Matt

 

[MikeFerrara]

Good point - got to consider the pp02 as well as the % to sustain life. I'm sure more of this will be learned from trimix certification. (Which I have not done yet).

--Matt

The %O2 or FO2 doesn't matter at all. All that matters is the PPO2.

Below 250 ft and down to about 400) we use 10/70 which, if truth be told, sometimes comes out to be more like 9/70 which is 9% O2 and 70% He. There's no problem breathing it below about 30 ft.

We don't breath it below a PPO2 of 0.18 ATA. They claim that 0.16 ATA PPO2 will sustain you but not it won't if you're doing very much.

 

[Gary D.]

What happens at 2065 feet? It's interesting that the current record is exactly one-half of that.

He came back up. So he covered the distance twice.

hehehe

Gary D.

 

[brssmnky]

I know someone did a 1000ft dive recently and just about got away with it.

Closed circuit rebreathing may expand this a bit but you're talking massive risks. There are absolute pressures where standard regulators would refuse to give gas but i dont think this is really an issue as other limiting factors like gas mix and so on would come into play well below that.

HPNS, O2 toxicity and a multitide of other factors are more likely to cause the physical maximum of a dive.

How deep can I go? Well not deep enough according to my last girlfriend! :cussing: no, seriously, I'm crying on the inside...
Actually, from what I understand the true "closed" circuit rebreathers (like what the US Navy uses) aren't rated to go deep at all... for the deeper dives and better bottom time you need the "partially" closed rebreathers (20% expelled per cycle) and I think tri-mix with helium helps with depth, too (but that adds to the DCS risks). Am I wrong? I'm not formally trained, just read magazines a lot. 1,000 ft? 2,000 ft? How many atmospheres is that? Gawd, the pressure's gotta be crazy... I don't know, I don't think I presonally would ever want to go deeper than 200 ft (er... is that 60m?)

 

[MikeFerrara]

Actually, from what I understand the true "closed" circuit rebreathers (like what the US Navy uses) aren't rated to go deep at all...

You're thinking of oxygen rebreathers. The reason you can't go very deep using them is because you're breathing pure oxygen.

for the deeper dives and better bottom time you need the "partially" closed rebreathers (20% expelled per cycle) and I think tri-mix with helium helps with depth, too (but that adds to the DCS risks). Am I wrong?

You are wrong on both counts. Gasses that are appropriate for deep diving can be used in both closed ciruit rebreathers and semi-closed circuit rebreathers.

Helium does not add to the risk of DCS. In fact the latest trend in decompression is to ride helium mixes all the way up to the switch to pure O2.

 

[Paul Evans]

I believe this record still stands ...

http://www.jolt.ca/scuba/index.php?option=news&task=viewarticle&sid=43

... Bob (Grateful Diver)

Yip, thats the current record on open circuit.

 

[Paul Evans]

1. At what point do gases become to thick to breath. if any?

2. After reading some articales on Mark Ellyat and the dive he did succsesfully and the prevoius dives that he was very lucky to return from, something was mentioned about pressure damage to his bones, in particular his skull?