Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover

mortenkjerulff · 26th May 2006, 08:14

Quote: (Originally Posted by SFM)

PMR: On this point, in statistical terms, do we have any idea of accidents risks with existing tables?
BG: Jean-Pierre Imbert, when he used to work for COMEX, realized a thorough study on the topic. Divers must know that one has to consider the amount of gas(es) to eliminate, an amount that is a function of the depth and the square root of the time spent at the bottom. One’s organism has to eliminate that(those) gas(es) and by nature it has its physiological limits. It requires time which cannot be reduced with impunity. Tables that can be downloaded like Varying Permeability Model (VPM) or Reduce Gradient Bubble Model (RGBM) correspond to decompression times we were using more than 30 years ago. The risk was then evaluated at 10%. With the current COMEX tables, for any depth and duration, we divided this risk by 10, meaning less than 1% accident rate. For comparison purposes, the risk for leisure/hobby diving is around 0.01% to 0.001% as long as one stays within the security curve… As soon as one reaches 20 to 30 minutes at 40m, the risk climbs to 0.1% and for 20 minutes at 60m we reach the 1% ratio, identical to what we currently have in our trimix tables… To sum up, one should be reasonable and be content with diving for less than 20 minutes at 60m on air and for trimix, less than 15 minutes at 80m. Ten more minutes yield a huge price to pay in terms of decompression. Dr (MD) Eric Bergman has noted that the number of tech divers treated for a decompression accident has been very high during the summer of 2005…

Could anyone explain me/us what the evaluated risk at 10% precisely means? It is surely not the actual risk of DCI.
Somewhere it was mentioned that this number should be divided by another (arbitrary?!) number?

I think this definition should be clear before we can discuss the article properly

Morten

rossh · 26th May 2006, 09:16

In reference to the comments in the original posted interview here:

The article mentions a 100m dive and the resulting deco. Bernard Gardette is quoted as saying internet software is only giving half the required 3 hours of a "1992" table. A test of this dive parameter in V-Planner and VPM-B, a typical 20 min bottom time (27 min RT) CCR dive. This will result in 190 minutes RT (3 hours 10 mins).

The second example 80m 40 mins on heliox. Again tested using V-Planner and VPM-B (with 40 min bottom time) a result of 3h 40mins deco vs. the quoted table of 4h 2min deco. 20 mins less, but not half as stated.

Maybe he is talking of another software product, however the allegations made are not valid against VPM-B (or even close).

Regards

rossh · 26th May 2006, 14:02

Quote: (Originally Posted by Drmike)

When I looked at a deco model for our 200m dive I compared the deco profile as given by VPMBE/RGBM to that given by traditional models and in all cases the shallow stops were considerably longer. I note that since its inception VPMB has evolved with increasingly longer shallow stops to something now which more refelcts the traditional algos.....

Some very interesting reading with comparison with Comex/vpm etc here
:-

Hello Mike,

I would point out some errors is the paper you reference.

The paper mentions VPM-B, when in fact the dives shown are old original VPM - hence the comparisons are not valid as described. I have emailed the author several times asking for, and suggesting corrections. That was a year ago now, but none have been amended.

I strongly disagree with any suggestions that CDM is in any way authoritive, binding, or superior to real deco models. Simply put; The CDM 18 is not a deco algorithm, and it is not a deco model. Its a collection of the longest possible times and simple timing formula, taken from an assortment of real deco models. Many have been validated in their own right. But making a matrix of the longest possible time from each one... not a valid model. CDM further appears to be fitted with hand crafted formula to make it produce a desired result in the deeper sections.
Does the CDM 18 have any basis for its own existence? Can it be considered an authoritive source of data? I don't believe so. CDM relies only on the simple principle "more deco time is alway better than less". At no point does it recognize sufficient deco on any one model or deco approach. It claims all deco models a failure, because they do not align with its combined, hand fabricated - longest possible time approach. I don't believe this kind of simplistic approach and test have a valid place.

On a different note.. for the really deep dives your doing - I recommend all the safety factors you can afford. However, lets not confuse desired deco, safety deco, cautious deco, with required deco. At the very deep depths, personal preference plays a big part. Some do a VPM-B/E straight out of the box, some even a straight VPM-B. Others want / need more.

Regards

divetheworld · 26th May 2006, 15:24

Quote: (Originally Posted by rossh)

On a different note.. for the really deep dives your doing - I recommend all the safety factors you can afford. However, lets not confuse desired deco, safety deco, cautious deco, with required deco. At the very deep depths, personal preference plays a big part. Some do a VPM-B/E straight out of the box, some even a straight VPM-B. Others want / need more.

Regards

Thats a bit of a chocolate fireguard statement. Dont get me wrong, I'm not here to dis you, but I did have higher expectations when I saw you post.
I would be more interested in your take on the MT92 tables, specifically in context that they are more suitable for long exposures.

Brent

Mark Chase · 26th May 2006, 15:38

Quote: (Originally Posted by divetheworld)

Thats a bit of a chocolate fireguard statement. Dont get me wrong, I'm not here to dis you, but I did have higher expectations when I saw you post.
I would be more interested in your take on the MT92 tables, specifically in context that they are more suitable for long exposures.

Brent

I have often herd it discussed and for reasons about which I have no hard facts I was always told that most tables were good to a max 100m 20min duration and after that it was all completely guess work.

I assumed some effort had been made at validation down to this depth but perhaps its just a myth.

One thing is for sure I have friends running 10/125GF dives and they are seemingly un bent but I feel shagged out and ache all over running 35/90

ATB

Mark Chase

***caveseeker7*** · 26th May 2006, 17:08

Quote: (Originally Posted by MHD)

I think you are mis-readig it, the following list is not conclusive but comes from my memory from 4 years of following Rebreather's and hopefully other people can correct as required

Deaths by model (these are from my memory only)

Cis lunar MK4/5 - 3 (could be more)
Meg - 8
Prism - 1
Inspo/Evo - about 30 (33-35?)
CCR1000/ Mk15 - 1
SMI 1600 / Mk15.5- 2 (I think, Dave Shaw and thought I'd heard of another)
Kiss (classic) - 0 (I can't remember any, not not to say there hasn't been one or more)
Kiss Sport - 0 as above
Rebreather-80 - 1 at least
EDO-04 and other clones- 1 at least
Halcyon fridge - 1
Ouroboros - 0

You missed three fatalities I could think of, I updated those.
AfaIk there were casualties in the military on MK series rigs.
Not an issue as the author of the COMEX report is going after rec/tec divers.

Mark LE8 · 26th May 2006, 17:56

Hello All,

The paper you mention was very upto date when it was written Ross - We are not your publicists! Obviously it was aimed at revealing weaknesses with certain products used as they might be by consumers. When the paper was written there was no way your program could have been used to provide adequte decompression i(n mine and many others opinion). The latest latest latest version you're hawking might possibly provide adequate decompression but only when used with a level of expertise not commonly found.

Why on earth do you still have conservatism settings that reflect the original nonsense? Why do you still allow people to 'select a bend' with 3 models and 5 levels of conservatism with each? Why dont you make a product that just gives adequate decompression - this is a science that is fairly well understood actually. I appreciate you may know nothing about decompression and are simply programming (well, i might add) some other crowds ideas. Surely there have been enough accidents on the umpteen re-incarnations of your software to now know what works and what doesnt? If you would like to see an approach that seems to work exceptionally well then buy a copy of decochek , read and study the support blurb and then try to write some decent predicting software rather than keep fixing the leaky boat that is the vpm model? And dont even get me started on the Really Good Bends Model!

Just back from a trip and a little fatigued - will dig out some funny emails about bubble model peddlers and their antics over the years.
Might open some eyes hopefully

but im sure it will just turn into a flan-fight/thread hijack and achieve nuttin as usual !!

Your serve...
regards...Mark

Has anyone read the book Ocean Gladiator yet? - its fantastic and has some fairly detailed accounts of duels with deep water/bubble models etc

Nitrogen Narcosis is for Christmas - Oxygen Toxicity is for life

Quote: (Originally Posted by rossh)

Hello Mike,

I would point out some errors is the paper you reference.

The paper mentions VPM-B, when in fact the dives shown are old original VPM - hence the comparisons are not valid as described. I have emailed the author several times asking for, and suggesting corrections. That was a year ago now, but none have been amended.

I strongly disagree with any suggestions that CDM is in any way authoritive, binding, or superior to real deco models. Simply put; The CDM 18 is not a deco algorithm, and it is not a deco model. Its a collection of the longest possible times and simple timing formula, taken from an assortment of real deco models. Many have been validated in their own right. But making a matrix of the longest possible time from each one... not a valid model. CDM further appears to be fitted with hand crafted formula to make it produce a desired result in the deeper sections.
Does the CDM 18 have any basis for its own existence? Can it be considered an authoritive source of data? I don't believe so. CDM relies only on the simple principle "more deco time is alway better than less". At no point does it recognize sufficient deco on any one model or deco approach. It claims all deco models a failure, because they do not align with its combined, hand fabricated - longest possible time approach. I don't believe this kind of simplistic approach and test have a valid place.

On a different note.. for the really deep dives your doing - I recommend all the safety factors you can afford. However, lets not confuse desired deco, safety deco, cautious deco, with required deco. At the very deep depths, personal preference plays a big part. Some do a VPM-B/E straight out of the box, some even a straight VPM-B. Others want / need more.

Regards

Mark LE8 · 26th May 2006, 18:32

Hi Mark,

I wouldnt really bother normally posting but I would like to comment on your post as its potentially full of nonsense

I hope people realise that 10/125 for arguements sake gives significantly less deco than say 30/65. Neither GF is relevant though. The GF becomes only relevant when matched against a specific profile.

60metres for 20 mins at 10/125 would save you 10-15 minutes and probably still be within tolerable (pain wise)exposures. However if you use the same GF on 60 for 60mins then you will be effectively shaving over an hour of the stops and this is a huge amount relative to the total (Im fully aware that the % is the same-despite the creme de menthe

)

25% off of 20mins shallow stop is 5 mins = no obvious bends and possibly even within realms of safety
The same 25% of 120mins shorter in the shallows however is 40mins. Missing this time may still give no apparent symptoms (pain) but you may have heard of osteonecrosis?

My point was, that stating various GF's is often detrimental to safety considering you might actually want ruined bones and others not. Something that MIGHT work again and again is 30/75 (air based) or 20/65 (helium) - again it is worth noting that GF's are not transferable between software packages, compare like for like and see

The same is true of with all the bubble model nonsense planners - relatively short duration dives can have 25-50% of the shallow stop time shaved without an obvious need for a wheelchair. When you do something larger though this same 50% can have an effect likened to lets say...explosive decompression.

Quote: (Originally Posted by Mark Chase)

I have often herd it discussed and for reasons about which I have no hard facts I was always told that most tables were good to a max 100m 20min duration and after that it was all completely guess work.

I assumed some effort had been made at validation down to this depth but perhaps its just a myth.

One thing is for sure I have friends running 10/125GF dives and they are seemingly un bent but I feel shagged out and ache all over running 35/90

ATB

Mark Chase

Mark Chase · 26th May 2006, 18:40

Quote: (Originally Posted by Mark LE8)

Hi Mark,

I would really bother normally posting but I would like to comment on your post.

I hope people realise that 10/125 for arguements sake gives significantly less deco than say 30/65. Neither GF is relevant though. The GF becomes only relevant when matched against a specific profile.

60metres for 20 mins at 10/125 would save you 10-15 minutes and probably still be within tolerable (pain wise)exposures. However if you use the same GF on 60 for 60mins then you will be effectively shaving over an hour of the stops and this is a huge amount relative to the total (Im fully aware that the % is the same-despite the creme de menth

)

25% off of 20mins shallow stop is 5 mins = no obvious bends and possibly even within realms of safety
The same 25% of 120mins shorter in the shallows however is 40mins. Missing this time may still give no apparent symptoms (pain) but you may have heard of osteo necrosis?

My point was, that stating various GF's is often detrimental to safety considering you might actually want ruined bones and others not. Something that MIGHT work again and again is 30/75 (air based) or 20/65 (helium) - again it is worth noting that GF's are not transferable between software packages, compare like for like and see

Hi Mark

What you doing on here? You hate rebreathers

I love my diving M8 but rest asured I like my old git 20/80 GFs

Well done for posting the WR with DIR thing. I laughed my tits off.

ATB

Mark Chase

Mark LE8 · 26th May 2006, 18:50

I just did a RB80 (clone) try dive ill have you know!

I didnt like the look of the single (17p)mushroom valve design that held my life in its hands bit. I suppose the dir guys have a little more faith than me though with all of the indoctrination ceremonies

Plus i got a ticket for both ybod's too! When i havent got water deep enough for the usual deep air fix I grab me a box to add a little spice.

;-)

Quote: (Originally Posted by Mark Chase)

Hi Mark

What you doing on here? You hate rebreathers

I love my diving M8 but rest asured I like my old git 20/80 GFs

Well done for posting the WR with DIR thing. I laughed my tits off.

ATB

Mark Chase

26th May 2006, 08:14	#61 (permalink)
mortenkjerulff Customise Me! Current Rebreather/s: Megalodon Other Rebreather/s: Not Bought Yet Join Date: Mar 2005 Location: Denmark Posts: 135	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Quote: (Originally Posted by SFM) PMR: On this point, in statistical terms, do we have any idea of accidents risks with existing tables? BG: Jean-Pierre Imbert, when he used to work for COMEX, realized a thorough study on the topic. Divers must know that one has to consider the amount of gas(es) to eliminate, an amount that is a function of the depth and the square root of the time spent at the bottom. One’s organism has to eliminate that(those) gas(es) and by nature it has its physiological limits. It requires time which cannot be reduced with impunity. Tables that can be downloaded like Varying Permeability Model (VPM) or Reduce Gradient Bubble Model (RGBM) correspond to decompression times we were using more than 30 years ago. The risk was then evaluated at 10%. With the current COMEX tables, for any depth and duration, we divided this risk by 10, meaning less than 1% accident rate. For comparison purposes, the risk for leisure/hobby diving is around 0.01% to 0.001% as long as one stays within the security curve… As soon as one reaches 20 to 30 minutes at 40m, the risk climbs to 0.1% and for 20 minutes at 60m we reach the 1% ratio, identical to what we currently have in our trimix tables… To sum up, one should be reasonable and be content with diving for less than 20 minutes at 60m on air and for trimix, less than 15 minutes at 80m. Ten more minutes yield a huge price to pay in terms of decompression. Dr (MD) Eric Bergman has noted that the number of tech divers treated for a decompression accident has been very high during the summer of 2005… Could anyone explain me/us what the evaluated risk at 10% precisely means? It is surely not the actual risk of DCI. Somewhere it was mentioned that this number should be divided by another (arbitrary?!) number? I think this definition should be clear before we can discuss the article properly Morten
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26th May 2006, 09:16	#62 (permalink)
rossh Custom Title Allowed! Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 106	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl In reference to the comments in the original posted interview here: The article mentions a 100m dive and the resulting deco. Bernard Gardette is quoted as saying internet software is only giving half the required 3 hours of a "1992" table. A test of this dive parameter in V-Planner and VPM-B, a typical 20 min bottom time (27 min RT) CCR dive. This will result in 190 minutes RT (3 hours 10 mins). The second example 80m 40 mins on heliox. Again tested using V-Planner and VPM-B (with 40 min bottom time) a result of 3h 40mins deco vs. the quoted table of 4h 2min deco. 20 mins less, but not half as stated. Maybe he is talking of another software product, however the allegations made are not valid against VPM-B (or even close). Regards __________________ Regards, Ross Hemingway V-Planner VPM-B Nitrox Trimix CCR Deco planning for Technical Divers www.v-planner.com
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26th May 2006, 14:02	#63 (permalink)
rossh Custom Title Allowed! Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 106	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Quote: (Originally Posted by Drmike) When I looked at a deco model for our 200m dive I compared the deco profile as given by VPMBE/RGBM to that given by traditional models and in all cases the shallow stops were considerably longer. I note that since its inception VPMB has evolved with increasingly longer shallow stops to something now which more refelcts the traditional algos..... Some very interesting reading with comparison with Comex/vpm etc here :- Hello Mike, I would point out some errors is the paper you reference. The paper mentions VPM-B, when in fact the dives shown are old original VPM - hence the comparisons are not valid as described. I have emailed the author several times asking for, and suggesting corrections. That was a year ago now, but none have been amended. I strongly disagree with any suggestions that CDM is in any way authoritive, binding, or superior to real deco models. Simply put; The CDM 18 is not a deco algorithm, and it is not a deco model. Its a collection of the longest possible times and simple timing formula, taken from an assortment of real deco models. Many have been validated in their own right. But making a matrix of the longest possible time from each one... not a valid model. CDM further appears to be fitted with hand crafted formula to make it produce a desired result in the deeper sections. Does the CDM 18 have any basis for its own existence? Can it be considered an authoritive source of data? I don't believe so. CDM relies only on the simple principle "more deco time is alway better than less". At no point does it recognize sufficient deco on any one model or deco approach. It claims all deco models a failure, because they do not align with its combined, hand fabricated - longest possible time approach. I don't believe this kind of simplistic approach and test have a valid place. On a different note.. for the really deep dives your doing - I recommend all the safety factors you can afford. However, lets not confuse desired deco, safety deco, cautious deco, with required deco. At the very deep depths, personal preference plays a big part. Some do a VPM-B/E straight out of the box, some even a straight VPM-B. Others want / need more. Regards __________________ Regards, Ross Hemingway V-Planner VPM-B Nitrox Trimix CCR Deco planning for Technical Divers www.v-planner.com
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26th May 2006, 15:24	#64 (permalink)
divetheworld Dive porn pimp Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Classic Kiss Other CCR Join Date: Mar 2005 Location: Leeds, England Posts: 1,551	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Quote: (Originally Posted by rossh) On a different note.. for the really deep dives your doing - I recommend all the safety factors you can afford. However, lets not confuse desired deco, safety deco, cautious deco, with required deco. At the very deep depths, personal preference plays a big part. Some do a VPM-B/E straight out of the box, some even a straight VPM-B. Others want / need more. Regards Thats a bit of a chocolate fireguard statement. Dont get me wrong, I'm not here to dis you, but I did have higher expectations when I saw you post. I would be more interested in your take on the MT92 tables, specifically in context that they are more suitable for long exposures. Brent __________________ Self praise is no reccomendation. Dont try to be a great man, just be a man and let history be the judge of you. CHECK OUT OUR INTERWEBS FOR CUSTOM REBREATHER UPGRADES *WWW.NARKEDAT90.CO.UK* *http://www.grpservices.com/pursuit/* Supporting Shearwater Research Products in Europe
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26th May 2006, 15:38	#65 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,540	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Quote: (Originally Posted by divetheworld) Thats a bit of a chocolate fireguard statement. Dont get me wrong, I'm not here to dis you, but I did have higher expectations when I saw you post. I would be more interested in your take on the MT92 tables, specifically in context that they are more suitable for long exposures. Brent I have often herd it discussed and for reasons about which I have no hard facts I was always told that most tables were good to a max 100m 20min duration and after that it was all completely guess work. I assumed some effort had been made at validation down to this depth but perhaps its just a myth. One thing is for sure I have friends running 10/125GF dives and they are seemingly un bent but I feel shagged out and ache all over running 35/90 ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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26th May 2006, 17:08	#66 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,419	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Quote: (Originally Posted by MHD) I think you are mis-readig it, the following list is not conclusive but comes from my memory from 4 years of following Rebreather's and hopefully other people can correct as required Deaths by model (these are from my memory only) Cis lunar MK4/5 - 3 (could be more) Meg - 8 Prism - 1 Inspo/Evo - about 30 (33-35?) CCR1000/ Mk15 - 1 SMI 1600 / Mk15.5- 2 (I think, Dave Shaw and thought I'd heard of another) Kiss (classic) - 0 (I can't remember any, not not to say there hasn't been one or more) Kiss Sport - 0 as above Rebreather-80 - 1 at least EDO-04 and other clones- 1 at least Halcyon fridge - 1 Ouroboros - 0 You missed three fatalities I could think of, I updated those. AfaIk there were casualties in the military on MK series rigs. Not an issue as the author of the COMEX report is going after rec/tec divers. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.'!" Last edited by caveseeker7 : 26th May 2006 at 18:08.
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26th May 2006, 17:56	#67 (permalink)
Mark LE8 New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: May 2006 Location: England Posts: 5	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Hello All, The paper you mention was very upto date when it was written Ross - We are not your publicists! Obviously it was aimed at revealing weaknesses with certain products used as they might be by consumers. When the paper was written there was no way your program could have been used to provide adequte decompression i(n mine and many others opinion). The latest latest latest version you're hawking might possibly provide adequate decompression but only when used with a level of expertise not commonly found. Why on earth do you still have conservatism settings that reflect the original nonsense? Why do you still allow people to 'select a bend' with 3 models and 5 levels of conservatism with each? Why dont you make a product that just gives adequate decompression - this is a science that is fairly well understood actually. I appreciate you may know nothing about decompression and are simply programming (well, i might add) some other crowds ideas. Surely there have been enough accidents on the umpteen re-incarnations of your software to now know what works and what doesnt? If you would like to see an approach that seems to work exceptionally well then buy a copy of decochek , read and study the support blurb and then try to write some decent predicting software rather than keep fixing the leaky boat that is the vpm model? And dont even get me started on the Really Good Bends Model! Just back from a trip and a little fatigued - will dig out some funny emails about bubble model peddlers and their antics over the years. Might open some eyes hopefully but im sure it will just turn into a flan-fight/thread hijack and achieve nuttin as usual !! Your serve... regards...Mark Has anyone read the book Ocean Gladiator yet? - its fantastic and has some fairly detailed accounts of duels with deep water/bubble models etc Nitrogen Narcosis is for Christmas - Oxygen Toxicity is for life Quote: (Originally Posted by rossh) Hello Mike, I would point out some errors is the paper you reference. The paper mentions VPM-B, when in fact the dives shown are old original VPM - hence the comparisons are not valid as described. I have emailed the author several times asking for, and suggesting corrections. That was a year ago now, but none have been amended. I strongly disagree with any suggestions that CDM is in any way authoritive, binding, or superior to real deco models. Simply put; The CDM 18 is not a deco algorithm, and it is not a deco model. Its a collection of the longest possible times and simple timing formula, taken from an assortment of real deco models. Many have been validated in their own right. But making a matrix of the longest possible time from each one... not a valid model. CDM further appears to be fitted with hand crafted formula to make it produce a desired result in the deeper sections. Does the CDM 18 have any basis for its own existence? Can it be considered an authoritive source of data? I don't believe so. CDM relies only on the simple principle "more deco time is alway better than less". At no point does it recognize sufficient deco on any one model or deco approach. It claims all deco models a failure, because they do not align with its combined, hand fabricated - longest possible time approach. I don't believe this kind of simplistic approach and test have a valid place. On a different note.. for the really deep dives your doing - I recommend all the safety factors you can afford. However, lets not confuse desired deco, safety deco, cautious deco, with required deco. At the very deep depths, personal preference plays a big part. Some do a VPM-B/E straight out of the box, some even a straight VPM-B. Others want / need more. Regards Last edited by Mark LE8 : 26th May 2006 at 18:00. Reason: fix typos
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26th May 2006, 18:32	#68 (permalink)
Mark LE8 New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: May 2006 Location: England Posts: 5	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Hi Mark, I wouldnt really bother normally posting but I would like to comment on your post as its potentially full of nonsense I hope people realise that 10/125 for arguements sake gives significantly less deco than say 30/65. Neither GF is relevant though. The GF becomes only relevant when matched against a specific profile. 60metres for 20 mins at 10/125 would save you 10-15 minutes and probably still be within tolerable (pain wise)exposures. However if you use the same GF on 60 for 60mins then you will be effectively shaving over an hour of the stops and this is a huge amount relative to the total (Im fully aware that the % is the same-despite the creme de menthe ) 25% off of 20mins shallow stop is 5 mins = no obvious bends and possibly even within realms of safety The same 25% of 120mins shorter in the shallows however is 40mins. Missing this time may still give no apparent symptoms (pain) but you may have heard of osteonecrosis? My point was, that stating various GF's is often detrimental to safety considering you might actually want ruined bones and others not. Something that MIGHT work again and again is 30/75 (air based) or 20/65 (helium) - again it is worth noting that GF's are not transferable between software packages, compare like for like and see The same is true of with all the bubble model nonsense planners - relatively short duration dives can have 25-50% of the shallow stop time shaved without an obvious need for a wheelchair. When you do something larger though this same 50% can have an effect likened to lets say...explosive decompression. Quote: (Originally Posted by Mark Chase) I have often herd it discussed and for reasons about which I have no hard facts I was always told that most tables were good to a max 100m 20min duration and after that it was all completely guess work. I assumed some effort had been made at validation down to this depth but perhaps its just a myth. One thing is for sure I have friends running 10/125GF dives and they are seemingly un bent but I feel shagged out and ache all over running 35/90 ATB Mark Chase Last edited by Mark LE8 : 26th May 2006 at 18:42.
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26th May 2006, 18:40	#69 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,540	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Quote: (Originally Posted by Mark LE8) Hi Mark, I would really bother normally posting but I would like to comment on your post. I hope people realise that 10/125 for arguements sake gives significantly less deco than say 30/65. Neither GF is relevant though. The GF becomes only relevant when matched against a specific profile. 60metres for 20 mins at 10/125 would save you 10-15 minutes and probably still be within tolerable (pain wise)exposures. However if you use the same GF on 60 for 60mins then you will be effectively shaving over an hour of the stops and this is a huge amount relative to the total (Im fully aware that the % is the same-despite the creme de menth ) 25% off of 20mins shallow stop is 5 mins = no obvious bends and possibly even within realms of safety The same 25% of 120mins shorter in the shallows however is 40mins. Missing this time may still give no apparent symptoms (pain) but you may have heard of osteo necrosis? My point was, that stating various GF's is often detrimental to safety considering you might actually want ruined bones and others not. Something that MIGHT work again and again is 30/75 (air based) or 20/65 (helium) - again it is worth noting that GF's are not transferable between software packages, compare like for like and see Hi Mark What you doing on here? You hate rebreathers I love my diving M8 but rest asured I like my old git 20/80 GFs Well done for posting the WR with DIR thing. I laughed my tits off. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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26th May 2006, 18:50	#70 (permalink)
Mark LE8 New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: May 2006 Location: England Posts: 5	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl I just did a RB80 (clone) try dive ill have you know! I didnt like the look of the single (17p)mushroom valve design that held my life in its hands bit. I suppose the dir guys have a little more faith than me though with all of the indoctrination ceremonies Plus i got a ticket for both ybod's too! When i havent got water deep enough for the usual deep air fix I grab me a box to add a little spice. ;-) Quote: (Originally Posted by Mark Chase) Hi Mark What you doing on here? You hate rebreathers I love my diving M8 but rest asured I like my old git 20/80 GFs Well done for posting the WR with DIR thing. I laughed my tits off. ATB Mark Chase
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