Will OC records always be deeper?

sasmedic · 24th December 2007, 08:12

Quote: (Originally Posted by OceanOpportunity)

physiology is physiology....HPNS is still a very real issue when using deep CCRs.

I agree, I wondered if a deep dive attempt is possible by combining OC and Rebreather to decrease the amount of time spent in water? I do not know how the record will be recoqnised? Will it count for the type of equipment you went to the depth with and would it matter if you come back with a RB for example?

sasmedic · 24th December 2007, 08:21

Quote: (Originally Posted by Abbo)

One thing I'd like to know is how surface-supplied divers have managed to overcome HPNS to dive beyond 330m?

On what gas, heliox? If so I would NOT know and an interesting question!!

Mdemon · 24th December 2007, 10:54

Quote: (Originally Posted by Dave Sutton)

Uhh....... I thought on some old Inspirations they *are* a part of the loop (like old KISS displays too...), a feature that (a) makes them pressure proof to infinity and (b) ensures eventual corrosion in the circuits?

In any event that does not seem to be the case on the crushed handsets here, but might lead to the confusion of the poster.

Dave

FWIW, yes, they are inside the loop on the Classic. The electronics is potted in a nice see-through rubbery stuff and the only exposed item is the microswitch which as you pointed out can corrode for various reasons (but a very cheap fix if you do it yourself). So they are at ambient and sealed. They aren't pressure proof to infinity though, since I think there are some airspaces in the components which may eventually lead to failure or pulling and breaking of joints. I imagine this will be veeeeeeeeeeeeeeeeery deep though.

The buzzer is the failure point. After 160m the chances go up that it fails in such a way that it disrupts the handsets. IIRC, Don Shirley had the Hammerhead so didn't have this particular problem. I can't remember how deep he went, but I think others have been to 220m in the Red Sea. I think they are rumoured to be the people who discovered the buzzer problem...

I think Rebreather's have been deeper than OC already, just not in the non-commercial world and not without a bell.

**Dave Sutton** · 24th December 2007, 15:48

Quote: (Originally Posted by Abbo)

One thing I'd like to know is how surface-supplied divers have managed to overcome HPNS to dive beyond 330m?

Slow compression. When we did the 1030 foot dive, we stowed the sat system at about 800 feet (need to go look at the logs) and then did excursions to working depth. Our time to 800 from zero was measured in hours, not minutes. Sat Super would stop compression as soon as anyone had a HPNS symptom and we would just sit and acclimate until it was gone and then start descent again. When we hit stow depth we rested for 12 hours before we got the first team ready for excursion. Deco was fixed obligation, so no need to hurry.

Just for interest, sort of on the same topic: we set PP02 by pressurizing the deck system to about 7 meters with air, and then blew down to stow depth with pure helium. Think of this like a rebreather with pure He diluent. There were electrically fan-driven scrubbers inside the deck chamber, about 25 CM diameter and perhaps 50 CM long, and these were changed every 12 hours or so by locking them out for scrubber change. Scrubber agent was Baralyme. C02 was not monitored. PP02 was monitored, but the means of maintaining PP02 was not based 'mainly' on PP02, but depth. As long as ambient temperature was not fluctuating too much, the sat techs just watched the stow depth, and as depth decreased (due to divers metabolizing the 02), pure 02 was added to mantain constant depth. Crosscheck was done to the 02 analizer. Interesting enough, they only had ONE 02 analizer cell on the system, and analized a one atmosphere sample gas that was released from the system with a needle valve and flowed over ONE sensor. Analizers were analog needle Beckman units. Sensors were changed "now and then".

Went into the scrapbook and found these, might be of interest. The first one is Mike Stubbs, one of our LST's (Life Support Technicians) at the sat console. Sort of center-right on the panel you can see the two Dwyer flowmeters to meter the sample gas to the 02 analizer. Second one is the logo for the sat system, the "Cachalot 1000", "Cachalot" being French for a deep diving whale, and "1000" for the design working depth. The "Cachalot 1" was the first experimental sat diving system manufactured by Westinghouse. Santa Fe bought the Westinghouse diving department and AFAIK was the first ever commercial operator of saturation diving systems anywhere (Smith Mountain dam project in 1965 was the first working sat job, the Newport Rhode Island Bridge was the first salt-water sat done, for the pile cutoffs).

I had posted the other two photos elsewhere here years ago, cannot remember where though, so forgive the re-post. The 3rd shot is a modified CCR-1000 used for sat bell-excursion work (this one by Harbor Branch for lockout from the JSL Submersible), circa 1979, and the helmet was the one used with the same system. Deep diving with this stuff is just an industrial process.

Dave (glad not to be offshore... memories of 5 Christmas's in a row at sea.....)

.

Meerveld · 25th December 2007, 04:27

Quote: (Originally Posted by Abbo)

One thing I'd like to know is how surface-supplied divers have managed to overcome HPNS to dive beyond 330m?

The consensus of opinion is that HPNS is caused by Helium compressing (or opposing the expansion of) the lipid layer during rapid increases in hydrostatic pressure. That is why the recommended strategy for combating the symptoms of HPNS is to slow or stop the descent to enable the pressure gradient across the lipid layer to reduce (equalise). Commercial divers avoid HPNS by pressurizing to depth very slowly. Unfortunately we cannot take a hours to get to depth

On the subject of "Will OC records always be deeper?", I believe that all records should be classified as SCUBA (Self Contained Underwater Breathing Apparatus). This covers both OC and CC. I believe that this trend towards defining divers as either OC or CC is promoting a dangerous mindset.

I consider myself to be just a DIVER, OC and CC are simply tools which I use to achieve my PRIMARY OBJECTIVE. My primary objective is the same for every dive, to get myself back to the surface ALIVE AND FIT enough to do the next dive. My belief is that a CCR combined with a full redundant OC bailout is the safest option. I regularly switch from CC to OC at 6 meters to accelerate deco on pure O2 and avoid the risk of breathing the loop of a MCCR hypoxic while struggling to get out of the water. I also switch to OC at the slightest hint of a problem with my CCR. Going back on the loop only when any issues are resolved. If any issues persist I turn and end the dive on OC. I know that this flies in the face of the hardcore CC crowd but I believe it is the best way of achieving my PRIMARY OBJECTIVE!

I consider that any World depth records would be best attempted on a combination of OC and CC. Utilising OC for the rapid descent and initial ascent. Switching to CC at the first deco stop to optimise decompression and minimise gas usage.

Regards,

Carl Meerveld

sasmedic · 25th December 2007, 07:25

Quote: (Originally Posted by Meerveld)

I believe that all records should be classified as SCUBA (Self Contained Underwater Breathing Apparatus). This covers both OC and CC. I believe that this trend towards defining divers as either OC or CC is promoting a dangerous mindset.

Hi carl, I agree with assessment!!!!

I wonder how the record registration process is working?? Is it defined by the person who registered it?? The surf control where I am hinders me from doing a good search on the subject?? Does anybody know out there??

I do not have a lot of time with the Rebreather yet but have made up my mind in terms of using OC as a back up like you mentioned.

Meerveld · 2nd January 2008, 11:47

Quote: (Originally Posted by sasmedic)

I wonder how the record registration process is working?? Is it defined by the person who registered it??

The problem with SCUBA diving records is that there is no organisation or association setting standards and officially recognising them.

I have discussed this with Mark Ellyatt (previous holder of the depth record). When he did his 313m dive the line he was descending was visibly deflected by currents and his depth gauge stopped working around 280m. So, although he pulled the 313m tag off the line even he cannot say for sure that the depth was correct. There are also other issues such as line stretch. Most lines stretch under tension. The more weight added to hold a line vertical against currents, the more stretch may be involved.

There will continue to be issues and disputes with SCUBA records until some credible organisation or association begins officially recognising them and establishes clear guidelines for their achievement.

On this topic we also need to consider if SCUBA diving records are even appropriate?

As with any debate there are numerous perspectives. On one side it could be said that record setters like Mark have inspired divers to expand there limits. Taking another view it can be argued that calling diving a sport and introducing competitive records is very dangerous. Attempting to run faster, jump higher or throw further in mainstream sports does not incur a significant risk of death or permanent disability. As divers, going deeper, penetrating further or deco'ing faster can significantly increase the risk of death or permanent disability.

This principle is well illustrated by the following:

"F.R.E.E. announces the following changes, to take effect immediately:

- The Unlimited Variable Ballast category has been permanently eliminated from our list of official competitive categories. No more requests for verification of record attempts on this category will be accepted. The current records, both male and female for fresh and salt water, will remain in our list of "Official Records" as the last performances verified and accepted for this form of freediving. We find that this category does not represent a true athletic achievement. Furthermore, due to recent events related to this category, which culminated with the tragic death of a diver attempting one of such records under the auspices of another organization, our Board of Directors has come to the decision that dives in this category are unacceptably risky and unsafe."

I just thought I would throw that into the debate

Carl

DaveB · 2nd January 2008, 15:57

I heard Don give a very good and interesting talk on this dive. From memory, he had done some pre-dive work on some oil filled part of his hammerhead electronics, but didn't have extra oil when he closed it up again. He theorized that a small air bubble was the culprit. (Heard the talk a few years ago, so this might not be completely right).

Quote: (Originally Posted by JOHNNY4FISH)

I DON'T UNDERSTAND THIS STATEMENT

"When Shaw did not come up for his planned meet, the back up diver for Shaw dived beyond his planned 250m when his buddy inspiration's electronics imploded at about 280m"

SINCE THE HANDSETS ARE PART OF THE BREATHING LOOP WHY WOULD THE HANDSETS IMPLODE? WHY NOT THE HOSES OR THE MOUTHPIECE? OR IS THIS JUST BS?

Inspired Trainer · 2nd January 2008, 18:47

Divers are a funny bunch...as soon as some have done their open waters they are planning 300metre dives. Similarly, some nursery slope skiers are planning black run fiascos that end in tears too. The more you train the more you get to realise just how far the goal is and only the most competent get very far. Competitions taking place underwater are not like Chess or Formation Ginger Bread Man making of course as the spills are generally life threatening.

Diving is an unusual sport that happens in an environment where failure means drowning or bends or AGE but some can 'compete' in it semi safely, with enough practise and support, just like driving cars fast though if you aint no good you gonna crash! Schumacher didnt practise only on the weekends and if thats all you got time for then be sensible and avoid chasing tigers tails.

Maybe a Rebreather will be used on an ultra deep dive successfully in the future but ive met 3 who died trying and ALL likely succumbed to IIOO (inexperience induced over optimism) compounded by stealthy CCR failure modes

When a kamikaze CCR pilot starts doing stunt dives without bailout then the 'record' books can have a sub chapter of CCR only - these chaps will have quite a niche im sure

Quote: (Originally Posted by Meerveld)

The problem with SCUBA diving records is that there is no organisation or association setting standards and officially recognising them.

I have discussed this with Mark Ellyatt (previous holder of the depth record). When he did his 313m dive the line he was descending was visibly deflected by currents and his depth gauge stopped working around 280m. So, although he pulled the 313m tag off the line even he cannot say for sure that the depth was correct. There are also other issues such as line stretch. Most lines stretch under tension. The more weight added to hold a line vertical against currents, the more stretch may be involved.

There will continue to be issues and disputes with SCUBA records until some credible organisation or association begins officially recognising them and establishes clear guidelines for their achievement.

On this topic we also need to consider if SCUBA diving records are even appropriate?

As with any debate there are numerous perspectives. On one side it could be said that record setters like Mark have inspired divers to expand there limits. Taking another view it can be argued that calling diving a sport and introducing competitive records is very dangerous. Attempting to run faster, jump higher or throw further in mainstream sports does not incur a significant risk of death or permanent disability. As divers, going deeper, penetrating further or deco'ing faster can significantly increase the risk of death or permanent disability.

This principle is well illustrated by the following:

"F.R.E.E. announces the following changes, to take effect immediately:

- The Unlimited Variable Ballast category has been permanently eliminated from our list of official competitive categories. No more requests for verification of record attempts on this category will be accepted. The current records, both male and female for fresh and salt water, will remain in our list of "Official Records" as the last performances verified and accepted for this form of freediving. We find that this category does not represent a true athletic achievement. Furthermore, due to recent events related to this category, which culminated with the tragic death of a diver attempting one of such records under the auspices of another organization, our Board of Directors has come to the decision that dives in this category are unacceptably risky and unsafe."

I just thought I would throw that into the debate

Carl

Abbo · 2nd January 2008, 23:44

The purpose of this thread was to ask where the sweet spot is where CC is safer than OC. Perhaps the reason for asking was a nagging doubt that it is more dangerous for all depths because there are too many things to go wrong. The vast majority of rebreather divers grudgingly admit that CC is more dangerous than OC at least up to the limits of air dil. At 100-150m, CC gives you more time to sort out problems, but more problems to sort out. Beyond that, depth substantially reduces scrubber life, and WOB becomes a problem. The point of asking about extreme depths was to better understand the risks I am taking - and intend to continue taking.

Is there a sweet spot?
Where does it end?
What ends it?

24th December 2007, 08:12	#21 (permalink)
sasmedic New Member Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Oct 2007 Location: South Africa Posts: 15	Re: Will OC records always be deeper? Quote: (Originally Posted by OceanOpportunity) physiology is physiology....HPNS is still a very real issue when using deep CCRs. I agree, I wondered if a deep dive attempt is possible by combining OC and Rebreather to decrease the amount of time spent in water? I do not know how the record will be recoqnised? Will it count for the type of equipment you went to the depth with and would it matter if you come back with a RB for example? __________________ The best cure for fear is knowledge!!!
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24th December 2007, 08:21	#22 (permalink)
sasmedic New Member Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Oct 2007 Location: South Africa Posts: 15	Re: Will OC records always be deeper? Quote: (Originally Posted by Abbo) One thing I'd like to know is how surface-supplied divers have managed to overcome HPNS to dive beyond 330m? On what gas, heliox? If so I would NOT know and an interesting question!! __________________ The best cure for fear is knowledge!!! Last edited by sasmedic : 25th December 2007 at 07:26.
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24th December 2007, 10:54	#23 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,926	Re: Will OC records always be deeper? Quote: (Originally Posted by Dave Sutton) Uhh....... I thought on some old Inspirations they are a part of the loop (like old KISS displays too...), a feature that (a) makes them pressure proof to infinity and (b) ensures eventual corrosion in the circuits? In any event that does not seem to be the case on the crushed handsets here, but might lead to the confusion of the poster. Dave FWIW, yes, they are inside the loop on the Classic. The electronics is potted in a nice see-through rubbery stuff and the only exposed item is the microswitch which as you pointed out can corrode for various reasons (but a very cheap fix if you do it yourself). So they are at ambient and sealed. They aren't pressure proof to infinity though, since I think there are some airspaces in the components which may eventually lead to failure or pulling and breaking of joints. I imagine this will be veeeeeeeeeeeeeeeeery deep though. The buzzer is the failure point. After 160m the chances go up that it fails in such a way that it disrupts the handsets. IIRC, Don Shirley had the Hammerhead so didn't have this particular problem. I can't remember how deep he went, but I think others have been to 220m in the Red Sea. I think they are rumoured to be the people who discovered the buzzer problem... I think Rebreather's have been deeper than OC already, just not in the non-commercial world and not without a bell. __________________ www.southwestmafia.com "small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!" The WRONG Attitude will get you killed. "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?" Last edited by Mdemon : 24th December 2007 at 10:58.
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25th December 2007, 04:27	#25 (permalink)
Meerveld Aviator, diver & sailor Current Rebreather/s: Pelagian Other Rebreather/s: Pelagian Join Date: Jul 2007 Location: Koh Samui, Thailand Posts: 30	Re: Will OC records always be deeper? Quote: (Originally Posted by Abbo) One thing I'd like to know is how surface-supplied divers have managed to overcome HPNS to dive beyond 330m? The consensus of opinion is that HPNS is caused by Helium compressing (or opposing the expansion of) the lipid layer during rapid increases in hydrostatic pressure. That is why the recommended strategy for combating the symptoms of HPNS is to slow or stop the descent to enable the pressure gradient across the lipid layer to reduce (equalise). Commercial divers avoid HPNS by pressurizing to depth very slowly. Unfortunately we cannot take a hours to get to depth On the subject of "Will OC records always be deeper?", I believe that all records should be classified as SCUBA (Self Contained Underwater Breathing Apparatus). This covers both OC and CC. I believe that this trend towards defining divers as either OC or CC is promoting a dangerous mindset. I consider myself to be just a DIVER, OC and CC are simply tools which I use to achieve my PRIMARY OBJECTIVE. My primary objective is the same for every dive, to get myself back to the surface ALIVE AND FIT enough to do the next dive. My belief is that a CCR combined with a full redundant OC bailout is the safest option. I regularly switch from CC to OC at 6 meters to accelerate deco on pure O2 and avoid the risk of breathing the loop of a MCCR hypoxic while struggling to get out of the water. I also switch to OC at the slightest hint of a problem with my CCR. Going back on the loop only when any issues are resolved. If any issues persist I turn and end the dive on OC. I know that this flies in the face of the hardcore CC crowd but I believe it is the best way of achieving my PRIMARY OBJECTIVE! I consider that any World depth records would be best attempted on a combination of OC and CC. Utilising OC for the rapid descent and initial ascent. Switching to CC at the first deco stop to optimise decompression and minimise gas usage. Regards, Carl Meerveld __________________ We do not inherit the earth from our parents; we steal it from our children ~ based on a Native American proverb Last edited by Meerveld : 25th December 2007 at 04:43.
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25th December 2007, 07:25	#26 (permalink)
sasmedic New Member Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Oct 2007 Location: South Africa Posts: 15	Re: Will OC records always be deeper? Quote: (Originally Posted by Meerveld) I believe that all records should be classified as SCUBA (Self Contained Underwater Breathing Apparatus). This covers both OC and CC. I believe that this trend towards defining divers as either OC or CC is promoting a dangerous mindset. Hi carl, I agree with assessment!!!! I wonder how the record registration process is working?? Is it defined by the person who registered it?? The surf control where I am hinders me from doing a good search on the subject?? Does anybody know out there?? I do not have a lot of time with the Rebreather yet but have made up my mind in terms of using OC as a back up like you mentioned. __________________ The best cure for fear is knowledge!!!
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2nd January 2008, 11:47	#27 (permalink)
Meerveld Aviator, diver & sailor Current Rebreather/s: Pelagian Other Rebreather/s: Pelagian Join Date: Jul 2007 Location: Koh Samui, Thailand Posts: 30	Re: Will OC records always be deeper? Quote: (Originally Posted by sasmedic) I wonder how the record registration process is working?? Is it defined by the person who registered it?? The problem with SCUBA diving records is that there is no organisation or association setting standards and officially recognising them. I have discussed this with Mark Ellyatt (previous holder of the depth record). When he did his 313m dive the line he was descending was visibly deflected by currents and his depth gauge stopped working around 280m. So, although he pulled the 313m tag off the line even he cannot say for sure that the depth was correct. There are also other issues such as line stretch. Most lines stretch under tension. The more weight added to hold a line vertical against currents, the more stretch may be involved. There will continue to be issues and disputes with SCUBA records until some credible organisation or association begins officially recognising them and establishes clear guidelines for their achievement. On this topic we also need to consider if SCUBA diving records are even appropriate? As with any debate there are numerous perspectives. On one side it could be said that record setters like Mark have inspired divers to expand there limits. Taking another view it can be argued that calling diving a sport and introducing competitive records is very dangerous. Attempting to run faster, jump higher or throw further in mainstream sports does not incur a significant risk of death or permanent disability. As divers, going deeper, penetrating further or deco'ing faster can significantly increase the risk of death or permanent disability. This principle is well illustrated by the following: "F.R.E.E. announces the following changes, to take effect immediately: - The Unlimited Variable Ballast category has been permanently eliminated from our list of official competitive categories. No more requests for verification of record attempts on this category will be accepted. The current records, both male and female for fresh and salt water, will remain in our list of "Official Records" as the last performances verified and accepted for this form of freediving. We find that this category does not represent a true athletic achievement. Furthermore, due to recent events related to this category, which culminated with the tragic death of a diver attempting one of such records under the auspices of another organization, our Board of Directors has come to the decision that dives in this category are unacceptably risky and unsafe." I just thought I would throw that into the debate Carl __________________ We do not inherit the earth from our parents; we steal it from our children ~ based on a Native American proverb Last edited by Meerveld : 2nd January 2008 at 16:20.
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2nd January 2008, 15:57	#28 (permalink)
DaveB Rebreather World Writer Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Belper, Derbyshire, UK Posts: 89	Re: Will OC records always be deeper? I heard Don give a very good and interesting talk on this dive. From memory, he had done some pre-dive work on some oil filled part of his hammerhead electronics, but didn't have extra oil when he closed it up again. He theorized that a small air bubble was the culprit. (Heard the talk a few years ago, so this might not be completely right). Quote: (Originally Posted by JOHNNY4FISH) I DON'T UNDERSTAND THIS STATEMENT "When Shaw did not come up for his planned meet, the back up diver for Shaw dived beyond his planned 250m when his buddy inspiration's electronics imploded at about 280m" SINCE THE HANDSETS ARE PART OF THE BREATHING LOOP WHY WOULD THE HANDSETS IMPLODE? WHY NOT THE HOSES OR THE MOUTHPIECE? OR IS THIS JUST BS? __________________ David
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2nd January 2008, 18:47	#29 (permalink)
Inspired Trainer New Member Current Rebreather/s: Pelagian Other Rebreather/s: Pelagian Join Date: Oct 2007 Location: London Posts: 63	Re: Will OC records always be deeper? Divers are a funny bunch...as soon as some have done their open waters they are planning 300metre dives. Similarly, some nursery slope skiers are planning black run fiascos that end in tears too. The more you train the more you get to realise just how far the goal is and only the most competent get very far. Competitions taking place underwater are not like Chess or Formation Ginger Bread Man making of course as the spills are generally life threatening. Diving is an unusual sport that happens in an environment where failure means drowning or bends or AGE but some can 'compete' in it semi safely, with enough practise and support, just like driving cars fast though if you aint no good you gonna crash! Schumacher didnt practise only on the weekends and if thats all you got time for then be sensible and avoid chasing tigers tails. Maybe a Rebreather will be used on an ultra deep dive successfully in the future but ive met 3 who died trying and ALL likely succumbed to IIOO (inexperience induced over optimism) compounded by stealthy CCR failure modes When a kamikaze CCR pilot starts doing stunt dives without bailout then the 'record' books can have a sub chapter of CCR only - these chaps will have quite a niche im sure Quote: (Originally Posted by Meerveld) The problem with SCUBA diving records is that there is no organisation or association setting standards and officially recognising them. I have discussed this with Mark Ellyatt (previous holder of the depth record). When he did his 313m dive the line he was descending was visibly deflected by currents and his depth gauge stopped working around 280m. So, although he pulled the 313m tag off the line even he cannot say for sure that the depth was correct. There are also other issues such as line stretch. Most lines stretch under tension. The more weight added to hold a line vertical against currents, the more stretch may be involved. There will continue to be issues and disputes with SCUBA records until some credible organisation or association begins officially recognising them and establishes clear guidelines for their achievement. On this topic we also need to consider if SCUBA diving records are even appropriate? As with any debate there are numerous perspectives. On one side it could be said that record setters like Mark have inspired divers to expand there limits. Taking another view it can be argued that calling diving a sport and introducing competitive records is very dangerous. Attempting to run faster, jump higher or throw further in mainstream sports does not incur a significant risk of death or permanent disability. As divers, going deeper, penetrating further or deco'ing faster can significantly increase the risk of death or permanent disability. This principle is well illustrated by the following: "F.R.E.E. announces the following changes, to take effect immediately: - The Unlimited Variable Ballast category has been permanently eliminated from our list of official competitive categories. No more requests for verification of record attempts on this category will be accepted. The current records, both male and female for fresh and salt water, will remain in our list of "Official Records" as the last performances verified and accepted for this form of freediving. We find that this category does not represent a true athletic achievement. Furthermore, due to recent events related to this category, which culminated with the tragic death of a diver attempting one of such records under the auspices of another organization, our Board of Directors has come to the decision that dives in this category are unacceptably risky and unsafe." I just thought I would throw that into the debate Carl Last edited by Inspired Trainer : 2nd January 2008 at 18:56.
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2nd January 2008, 23:44	#30 (permalink)
Abbo Nicholas Smith Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Aug 2006 Location: Tokyo Posts: 440	Re: Will OC records always be deeper? The purpose of this thread was to ask where the sweet spot is where CC is safer than OC. Perhaps the reason for asking was a nagging doubt that it is more dangerous for all depths because there are too many things to go wrong. The vast majority of rebreather divers grudgingly admit that CC is more dangerous than OC at least up to the limits of air dil. At 100-150m, CC gives you more time to sort out problems, but more problems to sort out. Beyond that, depth substantially reduces scrubber life, and WOB becomes a problem. The point of asking about extreme depths was to better understand the risks I am taking - and intend to continue taking. Is there a sweet spot? Where does it end? What ends it?
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