Question about DCIEM tables
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Dr Deco
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Hello Ome Ko:
As far as I am aware, there is not any difference. The commercial tables are for decompression diving and are calculated according to the Kid-Stubbs model of series compartments. NDLs come out of experiments to determine these tables. The recreational tables are a subset using only the NDLs.
Dr Deco :doctor:
As far as I am aware, there is not any difference. The commercial tables are for decompression diving and are calculated according to the Kid-Stubbs model of series compartments. NDLs come out of experiments to determine these tables. The recreational tables are a subset using only the NDLs.
Dr Deco :doctor:
Dr Deco
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Ome Ko:
One can always reduce the US Navy NDLs by a few minutes, and then you will have the PADI Tables - or whatever is in a similar time range.
One can always reduce the US Navy NDLs by a few minutes, and then you will have the PADI Tables - or whatever is in a similar time range.
Dr Deco:
I believe that statement is unintentionally misleading. I know you know the difference and this is merely a problem in communicating the concept. The PADI tables are not merely the US Navy tables with shorter NDLs. PADI tables have shorter NDLs than the Navy tables for most (but not all) depths, but they are also much more liberal than the Navy tables with respect to repetitive dives.
kbuschmann
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The 'Sport' tables are equivalent to Table 1S (the Short Standard Air Decompression Table). They are based on the same model and empirical data as the standard DCIEM tables. The only real difference between the Sport tables and the original tables is not with the actual tables themselves, but with the recommended algorithm for determining repetitive dive times. The Sport table directions give a somewhat more conservative solution. In the Canadian Navy we continue to use the original method. By the way, DCIEM is now called DRDC. New Heliox tables are being tested as we speak.
Dr Deco
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Hello Walter and Readers:
PADI
The NDLs in the PADI tables were taken from the work of Dr Merrill Spencer and Dave Johanson where they determined minimal gas bubbles in the dive subjects as detected by the Doppler ultrasound bubble detector. The NDLs therefore are not reduced arbitrarily by a set amount but rather adjusted based on these empirical tests.
The NDLs could, in some cases, be more liberal than those of the US Navy. The Navy, curiously enough, did not actually determine NDLs; they came from tests of decompression tables.
Repetitive Diving
There are many ways to calculate a repetitive dive, and , without a computer, none of them is easy. They require tables showing the gas loads for your dive, and tables for the off gassing during the surface interval, and then new tables for the repetitive dive based on the gas loads at the conclusion of the surface interval.
Clearly, that is not simple and would require a huge book of tables. Most impractical. Thus, as a simplification, the next dive is based on the off gassing of the slowest tissue that could load in any dive for the diver population. Using this system, a single, simple repetitive dive card can be constructed based on groups (Letter Groups). BSAC uses a different system, as does NAUI for recreational diving.
Because the US Navy is primarily focused on surface supplied diving, bottom times are not limited. Indeed, dives can sometimes be long and/or deep. The longest compartment that can load in their scenarios is the 120-minute halftime compartment.
Off gassing is calculated for this compartment time, and it will cover all situations. Recreational diving is SCUBA and limited to no decompression rules. The 120-minute compartment does not load under these conditions (usually). The gas loads with the 60-minute compartment being the longest. Off gassing and repetitive tables are based on the 60-minute compartment for PADI tables. Computers will actually calculate the compartment loads, and these are shorter than the 60-minute compartment for NDL diving.
Yes, the name has changed and is now Defence Research and Development Canada. Everyone I once knew there has gone including the name.
Dr Deco :doctor
PADI
The NDLs in the PADI tables were taken from the work of Dr Merrill Spencer and Dave Johanson where they determined minimal gas bubbles in the dive subjects as detected by the Doppler ultrasound bubble detector. The NDLs therefore are not reduced arbitrarily by a set amount but rather adjusted based on these empirical tests.
The NDLs could, in some cases, be more liberal than those of the US Navy. The Navy, curiously enough, did not actually determine NDLs; they came from tests of decompression tables.
Repetitive Diving
There are many ways to calculate a repetitive dive, and , without a computer, none of them is easy. They require tables showing the gas loads for your dive, and tables for the off gassing during the surface interval, and then new tables for the repetitive dive based on the gas loads at the conclusion of the surface interval.
Clearly, that is not simple and would require a huge book of tables. Most impractical. Thus, as a simplification, the next dive is based on the off gassing of the slowest tissue that could load in any dive for the diver population. Using this system, a single, simple repetitive dive card can be constructed based on groups (Letter Groups). BSAC uses a different system, as does NAUI for recreational diving.
Because the US Navy is primarily focused on surface supplied diving, bottom times are not limited. Indeed, dives can sometimes be long and/or deep. The longest compartment that can load in their scenarios is the 120-minute halftime compartment.
Off gassing is calculated for this compartment time, and it will cover all situations. Recreational diving is SCUBA and limited to no decompression rules. The 120-minute compartment does not load under these conditions (usually). The gas loads with the 60-minute compartment being the longest. Off gassing and repetitive tables are based on the 60-minute compartment for PADI tables. Computers will actually calculate the compartment loads, and these are shorter than the 60-minute compartment for NDL diving.
Yes, the name has changed and is now Defence Research and Development Canada. Everyone I once knew there has gone including the name.
Dr Deco :doctor
kbuschmann
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Dr Deco
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That is nice to hear that Ron is still there. I have not seen him in several years.
Thanks for all your helpful replies!
May I conclude that according to the DRDC-sports-tables repetitive recreational diving is more dangerous in terms of decompression sickness than repetitive professional diving?
BTW: In what organisation is "recreational diving limited to no decompression rules"? I'm allowed to do in-water decompression by CMAS last time I looked [which was - I admit - 15 years ago].
May I conclude that according to the DRDC-sports-tables repetitive recreational diving is more dangerous in terms of decompression sickness than repetitive professional diving?
BTW: In what organisation is "recreational diving limited to no decompression rules"? I'm allowed to do in-water decompression by CMAS last time I looked [which was - I admit - 15 years ago].
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