When could ? or should ? helium be added to a deco mix and is supersaturation a factor in hitting a 50/25/25 mix @ 70 ft.I have heard that people add he to avoid skin hits and or isobaric counterdifusionshould the he be treated as n2 in respect to loading,and in reality will it bend you or ? Thank you for your time !
Deco Gases
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triton94949
Guest
I will look forward to Dr Deco's reply to you. His answers are rich in theory.
Some divers add HE to their EAN50 making it TMX 50/25. There are claims that this makes them feel better. In reality, I would guess that since their deco program will make them stay longer on deco due to the HE in the deco mix, then that is why they feel better, because they are doing longer deco.
HE is normally added to the 30% deco mix, as in TMX 30/30.
You could (as I do) also add HE to your 20% deco mix, as in TMX 20/40.
Here is an example of a deco plan using TMX 10/70 with deco mixes of TMX 20/40, TMX 30/30, EAN50, and 100% O2.
This program is copyrighted, but it is slightly out of date, so hopefully none of the mod squad will get bent out of shape over it. It illustrates perfectly the answer to your question from a practical deco planning perspective.
DIVE PLAN
Dec to 100ft (2) on Trimix 30/30, 50ft/min descent.
Dec to 350ft (7) on Trimix 10.0/70.0, 60ft/min descent.
Level 350ft 8:30 (15) on Trimix 10.0/70.0, 1.16 ppO2, 64ft ead, 82ft end
Asc to 270ft (17) on Trimix 10.0/70.0, -30ft/min ascent.
Stop at 270ft 0:20 (18) on Trimix 10.0/70.0, 0.92 ppO2, 44ft ead, 58ft end
Stop at 260ft 1:00 (19) on Trimix 10.0/70.0, 0.89 ppO2, 41ft ead, 55ft end
Stop at 250ft 1:00 (20) on Trimix 10.0/70.0, 0.86 ppO2, 39ft ead, 52ft end
Stop at 240ft 1:00 (21) on Trimix 10.0/70.0, 0.83 ppO2, 36ft ead, 49ft end
Stop at 230ft 1:00 (22) on Trimix 10.0/70.0, 0.80 ppO2, 34ft ead, 46ft end
Stop at 220ft 1:00 (23) on Trimix 10.0/70.0, 0.77 ppO2, 31ft ead, 43ft end
Stop at 210ft 1:00 (24) on Trimix 10.0/70.0, 0.74 ppO2, 28ft ead, 40ft end
Stop at 200ft 1:00 (25) on Trimix 10.0/70.0, 0.70 ppO2, 26ft ead, 37ft end
Stop at 190ft 1:00 (26) on Trimix 20.0/40.0, 1.35 ppO2, 80ft ead, 101ft end
Stop at 180ft 1:00 (27) on Trimix 20.0/40.0, 1.29 ppO2, 75ft ead, 95ft end
Stop at 170ft 1:00 (28) on Trimix 20.0/40.0, 1.23 ppO2, 70ft ead, 89ft end
Stop at 160ft 1:00 (29) on Trimix 20.0/40.0, 1.17 ppO2, 65ft ead, 83ft end
Stop at 150ft 1:00 (30) on Trimix 20.0/40.0, 1.11 ppO2, 60ft ead, 77ft end
Stop at 140ft 2:00 (32) on Trimix 20.0/40.0, 1.05 ppO2, 55ft ead, 71ft end
Stop at 130ft 1:00 (33) on Trimix 30.0/30.0, 1.48 ppO2, 49ft ead, 81ft end
Stop at 120ft 2:00 (35) on Trimix 30.0/30.0, 1.39 ppO2, 44ft ead, 74ft end
Stop at 110ft 2:00 (37) on Trimix 30.0/30.0, 1.30 ppO2, 39ft ead, 67ft end
Stop at 100ft 2:00 (39) on Trimix 30.0/30.0, 1.21 ppO2, 34ft ead, 60ft end
Stop at 90ft 3:00 (42) on Trimix 30.0/30.0, 1.12 ppO2, 29ft ead, 53ft end
Stop at 80ft 4:00 (46) on Trimix 30.0/30.0, 1.03 ppO2, 24ft ead, 46ft end
Stop at 70ft 3:00 (49) on Nitrox 50.0, 1.56 ppO2, 32ft ead
Stop at 60ft 4:00 (53) on Nitrox 50.0, 1.41 ppO2, 26ft ead
Stop at 50ft 6:00 (59) on Nitrox 50.0, 1.26 ppO2, 20ft ead
Stop at 40ft 7:00 (66) on Nitrox 50.0, 1.10 ppO2, 13ft ead
Stop at 30ft 11:00 (77) on Nitrox 50.0, 0.95 ppO2, 7ft ead
Stop at 20ft 36:00 (113) on Oxygen, 1.60 ppO2, 0ft ead
Asc to sfc. (113) on Oxygen, -30ft/min ascent.
Off gassing starts at 289.4ft
OTU's this dive: 151
CNS Total: 67.3%
155.6 cu ft Trimix 10.0/70.0
20.4 cu ft Trimix 20.0/40.0
27.7 cu ft Trimix 30.0/30.0
35.9 cu ft Nitrox 50.0
26.7 cu ft Oxygen
266.4 cu ft TOTAL
Do you see where the HE comes in for the deco mixes? When it is needed.
It is definitely not needed at 20 ft.
It is probably not needed at 70 ft either.
Therefore you would likely not introduce HE into your deco mixes shallower than 80 ft. And before your 70 ft stop, you would have HE in all of your deco mixes.
I have not given you any theoretical answers. What I have done is shown you what the deco software tells you to do, regarding covering the decompression range with a combination of deco mixes that gradually increases the oxygen fraction and decreases the helium fraction. Given this particular deco algorithm, the measure of its success is in the 113 minutes of total dive time it requires to deliver this particular MOD and bottom time. If you could find a mix of gasses that gives you the same depth and bottom time at the cost of less deco time, then that would tell you which mix of gasses is the best.
Counter diffusion is what is happening as you increase the ppN2 during the decompression plan and decrease the ppHE. I am not aware of any realistic problems arising from counter diffusion.
Dr. Deco will likely give you a more theoretical justification, on the other hand, than I ever could.
Some divers add HE to their EAN50 making it TMX 50/25. There are claims that this makes them feel better. In reality, I would guess that since their deco program will make them stay longer on deco due to the HE in the deco mix, then that is why they feel better, because they are doing longer deco.
HE is normally added to the 30% deco mix, as in TMX 30/30.
You could (as I do) also add HE to your 20% deco mix, as in TMX 20/40.
Here is an example of a deco plan using TMX 10/70 with deco mixes of TMX 20/40, TMX 30/30, EAN50, and 100% O2.
This program is copyrighted, but it is slightly out of date, so hopefully none of the mod squad will get bent out of shape over it. It illustrates perfectly the answer to your question from a practical deco planning perspective.
DIVE PLAN
Dec to 100ft (2) on Trimix 30/30, 50ft/min descent.
Dec to 350ft (7) on Trimix 10.0/70.0, 60ft/min descent.
Level 350ft 8:30 (15) on Trimix 10.0/70.0, 1.16 ppO2, 64ft ead, 82ft end
Asc to 270ft (17) on Trimix 10.0/70.0, -30ft/min ascent.
Stop at 270ft 0:20 (18) on Trimix 10.0/70.0, 0.92 ppO2, 44ft ead, 58ft end
Stop at 260ft 1:00 (19) on Trimix 10.0/70.0, 0.89 ppO2, 41ft ead, 55ft end
Stop at 250ft 1:00 (20) on Trimix 10.0/70.0, 0.86 ppO2, 39ft ead, 52ft end
Stop at 240ft 1:00 (21) on Trimix 10.0/70.0, 0.83 ppO2, 36ft ead, 49ft end
Stop at 230ft 1:00 (22) on Trimix 10.0/70.0, 0.80 ppO2, 34ft ead, 46ft end
Stop at 220ft 1:00 (23) on Trimix 10.0/70.0, 0.77 ppO2, 31ft ead, 43ft end
Stop at 210ft 1:00 (24) on Trimix 10.0/70.0, 0.74 ppO2, 28ft ead, 40ft end
Stop at 200ft 1:00 (25) on Trimix 10.0/70.0, 0.70 ppO2, 26ft ead, 37ft end
Stop at 190ft 1:00 (26) on Trimix 20.0/40.0, 1.35 ppO2, 80ft ead, 101ft end
Stop at 180ft 1:00 (27) on Trimix 20.0/40.0, 1.29 ppO2, 75ft ead, 95ft end
Stop at 170ft 1:00 (28) on Trimix 20.0/40.0, 1.23 ppO2, 70ft ead, 89ft end
Stop at 160ft 1:00 (29) on Trimix 20.0/40.0, 1.17 ppO2, 65ft ead, 83ft end
Stop at 150ft 1:00 (30) on Trimix 20.0/40.0, 1.11 ppO2, 60ft ead, 77ft end
Stop at 140ft 2:00 (32) on Trimix 20.0/40.0, 1.05 ppO2, 55ft ead, 71ft end
Stop at 130ft 1:00 (33) on Trimix 30.0/30.0, 1.48 ppO2, 49ft ead, 81ft end
Stop at 120ft 2:00 (35) on Trimix 30.0/30.0, 1.39 ppO2, 44ft ead, 74ft end
Stop at 110ft 2:00 (37) on Trimix 30.0/30.0, 1.30 ppO2, 39ft ead, 67ft end
Stop at 100ft 2:00 (39) on Trimix 30.0/30.0, 1.21 ppO2, 34ft ead, 60ft end
Stop at 90ft 3:00 (42) on Trimix 30.0/30.0, 1.12 ppO2, 29ft ead, 53ft end
Stop at 80ft 4:00 (46) on Trimix 30.0/30.0, 1.03 ppO2, 24ft ead, 46ft end
Stop at 70ft 3:00 (49) on Nitrox 50.0, 1.56 ppO2, 32ft ead
Stop at 60ft 4:00 (53) on Nitrox 50.0, 1.41 ppO2, 26ft ead
Stop at 50ft 6:00 (59) on Nitrox 50.0, 1.26 ppO2, 20ft ead
Stop at 40ft 7:00 (66) on Nitrox 50.0, 1.10 ppO2, 13ft ead
Stop at 30ft 11:00 (77) on Nitrox 50.0, 0.95 ppO2, 7ft ead
Stop at 20ft 36:00 (113) on Oxygen, 1.60 ppO2, 0ft ead
Asc to sfc. (113) on Oxygen, -30ft/min ascent.
Off gassing starts at 289.4ft
OTU's this dive: 151
CNS Total: 67.3%
155.6 cu ft Trimix 10.0/70.0
20.4 cu ft Trimix 20.0/40.0
27.7 cu ft Trimix 30.0/30.0
35.9 cu ft Nitrox 50.0
26.7 cu ft Oxygen
266.4 cu ft TOTAL
Do you see where the HE comes in for the deco mixes? When it is needed.
It is definitely not needed at 20 ft.
It is probably not needed at 70 ft either.
Therefore you would likely not introduce HE into your deco mixes shallower than 80 ft. And before your 70 ft stop, you would have HE in all of your deco mixes.
I have not given you any theoretical answers. What I have done is shown you what the deco software tells you to do, regarding covering the decompression range with a combination of deco mixes that gradually increases the oxygen fraction and decreases the helium fraction. Given this particular deco algorithm, the measure of its success is in the 113 minutes of total dive time it requires to deliver this particular MOD and bottom time. If you could find a mix of gasses that gives you the same depth and bottom time at the cost of less deco time, then that would tell you which mix of gasses is the best.
Counter diffusion is what is happening as you increase the ppN2 during the decompression plan and decrease the ppHE. I am not aware of any realistic problems arising from counter diffusion.
Dr. Deco will likely give you a more theoretical justification, on the other hand, than I ever could.
lamont
Contributor
HolgerS
Guest
@ Triton
I disagree.
@ all
There are several sources promoting high He-content in decompression gases up to shallow depth. One of the biggest promoter - and one of the most disliked one - is George Irvine who conducted with his group real deco dives which are much faster than conventional deco tables with conventional deco gases would allow. Scientific bubble tests of the divers showed, they are clean. Another well-known promoter is Bruce Wienke, who describes He benefits in decompression in his books, e.g. "Decompression theory and application".
From science to practical reasons:
# Ascending doing deco, your body faces an N2-increase after gas switches. This is exactly, what you want to avoid during deco.
Example: 15/60 (N2 25%) from 75m to 21m than switch to EAN50 (N2 50%) at 21m: N2 incease in breathing gas
# Bubble cinetics getting better with He. He is less soluble, has higher difussion speed. He-bubbles have different laplace tension, He-bubbles are smaller. This leads to high bubble pressures and thus to less trapped inertgas and high rates of gas transfer from bubbles into tissue solution before being breathed "out".
# Blood cell rigidity increases with high N2-content, decreases with high He-content. For good decompression, good perfusion of cappilaries are crucial. With high blood cell rigiditiy, most blood cells cannot go through the finest cappilaries.
One of the mistakes of triton:
# He is penalized by decompression SW due to very conservative He-parameters from Keller/Bühlmann. This is known today. Unfortunately, noone spends money into publich decompression science, so this parameters are still used. Most people cheat their deco SW by handling e.g. 50/25 as EAN 50. So, they don´t have longer decompression. They still feel better.
This leads to overall recommendation:
# N2 content should be held stable or decreased by each gas switch during decompression. E.g.
15/55 (30%)
35/35 (30%)
50/25 (25%)
O2 (0%)
Hope that helps
HolgerS
I disagree.
@ all
There are several sources promoting high He-content in decompression gases up to shallow depth. One of the biggest promoter - and one of the most disliked one - is George Irvine who conducted with his group real deco dives which are much faster than conventional deco tables with conventional deco gases would allow. Scientific bubble tests of the divers showed, they are clean. Another well-known promoter is Bruce Wienke, who describes He benefits in decompression in his books, e.g. "Decompression theory and application".
From science to practical reasons:
# Ascending doing deco, your body faces an N2-increase after gas switches. This is exactly, what you want to avoid during deco.
Example: 15/60 (N2 25%) from 75m to 21m than switch to EAN50 (N2 50%) at 21m: N2 incease in breathing gas
# Bubble cinetics getting better with He. He is less soluble, has higher difussion speed. He-bubbles have different laplace tension, He-bubbles are smaller. This leads to high bubble pressures and thus to less trapped inertgas and high rates of gas transfer from bubbles into tissue solution before being breathed "out".
# Blood cell rigidity increases with high N2-content, decreases with high He-content. For good decompression, good perfusion of cappilaries are crucial. With high blood cell rigiditiy, most blood cells cannot go through the finest cappilaries.
One of the mistakes of triton:
# He is penalized by decompression SW due to very conservative He-parameters from Keller/Bühlmann. This is known today. Unfortunately, noone spends money into publich decompression science, so this parameters are still used. Most people cheat their deco SW by handling e.g. 50/25 as EAN 50. So, they don´t have longer decompression. They still feel better.
This leads to overall recommendation:
# N2 content should be held stable or decreased by each gas switch during decompression. E.g.
15/55 (30%)
35/35 (30%)
50/25 (25%)
O2 (0%)
Hope that helps
HolgerS
triton94949
Guest
HolgerS:
I never did get what his particular credentials were. I head that he does not work on the WKK project anymore. But besides being a stockbroker, I never heard nor read about his particular expertise. I don't supposed anyone knows? Undergrad chem maybe? Grad physics? Ph.D.? Stockbroker? This guys name comes up a lot, but there is no credible bio that is ever offered.
I have read books by Dr. Bruce Weinke. You can google him and find his books and get his bio.
I have read books by Gary Gentile. Google him and you come up with a library of shipwreck books. Gary Gentile is my favorite author. He loves to explain about the unexpected things that went wrong on some of the dives, and they make you think about what would you do in the same circumstances.
Google Irvine and all you get is a bunch of discourses. That is not the same as credentials. That is merely utterances. You have chosen him as your authority in the field, but unfortunately your authority is authority-less, or so it would seem. Sure, you can go on listening to him talk, but at some point you have to ask yourself, where does he get all this stuff? Just pulling it out of ... [thin air]? If so, then that is not "research."
triton94949
Guest
HolgerS:
If I run your combination of mixes for a dive to 230 fsw for 25 mins bottom time, then I get a total dive time of 101 minutes including decompression with your mixes.
If I substitute my deco mixes (TMX 30/30, EAN50, and 100%O2) for your deco mixes, I save 11 minutes from the total dive time. See the comparisons below.
The 11 minute differential suggests that your combination of mixes is less efficient, n'est pas (nicht wahr?)
Why don't you try running them both on YOUR software as well Holger, and then get back to us about what your comparative dive plans show up as? What is the differential when using your software?
YOUR MIXES:
DIVE PLAN
Dec to 100ft (4) on Trimix 35/35, 50ft/min descent.
Dec to 230ft (4) on Trimix 15.0/55.0, 60ft/min descent.
Level 230ft 20:30 (25) on Trimix 15.0/55.0, 1.19 ppO2, 67ft ead, 85ft end
Asc to 160ft (27) on Trimix 15.0/55.0, -30ft/min ascent.
Stop at 160ft 0:40 (28) on Trimix 15.0/55.0, 0.88 ppO2, 40ft ead, 54ft end
Stop at 150ft 1:00 (29) on Trimix 15.0/55.0, 0.83 ppO2, 36ft ead, 49ft end
Stop at 140ft 1:00 (30) on Trimix 15.0/55.0, 0.79 ppO2, 33ft ead, 45ft end
Stop at 130ft 1:00 (31) on Trimix 15.0/55.0, 0.74 ppO2, 29ft ead, 40ft end
Stop at 120ft 2:00 (33) on Trimix 15.0/55.0, 0.69 ppO2, 25ft ead, 36ft end
Stop at 110ft 2:00 (35) on Trimix 15.0/55.0, 0.65 ppO2, 21ft ead, 31ft end
Stop at 100ft 2:00 (37) on Trimix 35.0/35.0, 1.41 ppO2, 17ft ead, 53ft end
Stop at 90ft 2:00 (39) on Trimix 35.0/35.0, 1.30 ppO2, 14ft ead, 47ft end
Stop at 80ft 3:00 (42) on Trimix 35.0/35.0, 1.20 ppO2, 10ft ead, 40ft end
Stop at 70ft 3:00 (45) on Trimix 50.0/25.0, 1.56 ppO2, 0ft ead, 44ft end
Stop at 60ft 4:00 (49) on Trimix 50.0/25.0, 1.41 ppO2, 0ft ead, 37ft end
Stop at 50ft 4:00 (53) on Trimix 50.0/25.0, 1.26 ppO2, 0ft ead, 29ft end
Stop at 40ft 8:00 (61) on Trimix 50.0/25.0, 1.10 ppO2, 0ft ead, 22ft end
Stop at 30ft 10:00 (71) on Trimix 50.0/25.0, 0.95 ppO2, 0ft ead, 14ft end
Stop at 20ft 30:00 (101) on Oxygen, 1.45 ppO2, 0ft ead
Asc to sfc. (101) on Oxygen, -30ft/min ascent.
Off gassing starts at 184.3ft
OTU's this dive: 135
CNS Total: 59.7%
MY MIXES:
DIVE PLAN
Dec to 100ft (4) on Trimix 30/30, 50ft/min descent.
Dec to 230ft (4) on Trimix 15.0/55.0, 60ft/min descent.
Level 230ft 20:30 (25) on Trimix 15.0/55.0, 1.19 ppO2, 67ft ead, 85ft end
Asc to 160ft (27) on Trimix 15.0/55.0, -30ft/min ascent.
Stop at 160ft 0:40 (28) on Trimix 15.0/55.0, 0.88 ppO2, 40ft ead, 54ft end
Stop at 150ft 1:00 (29) on Trimix 15.0/55.0, 0.83 ppO2, 36ft ead, 49ft end
Stop at 140ft 1:00 (30) on Trimix 15.0/55.0, 0.79 ppO2, 33ft ead, 45ft end
Stop at 130ft 1:00 (31) on Trimix 30.0/30.0, 1.48 ppO2, 49ft ead, 81ft end
Stop at 120ft 1:00 (32) on Trimix 30.0/30.0, 1.39 ppO2, 44ft ead, 74ft end
Stop at 110ft 1:00 (33) on Trimix 30.0/30.0, 1.30 ppO2, 39ft ead, 67ft end
Stop at 100ft 2:00 (35) on Trimix 30.0/30.0, 1.21 ppO2, 34ft ead, 60ft end
Stop at 90ft 2:00 (37) on Trimix 30.0/30.0, 1.12 ppO2, 29ft ead, 53ft end
Stop at 80ft 2:00 (39) on Trimix 30.0/30.0, 1.03 ppO2, 24ft ead, 46ft end
Stop at 70ft 3:00 (42) on Nitrox 50.0, 1.56 ppO2, 32ft ead
Stop at 60ft 3:00 (45) on Nitrox 50.0, 1.41 ppO2, 26ft ead
Stop at 50ft 4:00 (49) on Nitrox 50.0, 1.26 ppO2, 20ft ead
Stop at 40ft 5:00 (54) on Nitrox 50.0, 1.10 ppO2, 13ft ead
Stop at 30ft 8:00 (62) on Nitrox 50.0, 0.95 ppO2, 7ft ead
Stop at 20ft 28:00 (90) on Oxygen, 1.45 ppO2, 0ft ead
Asc to sfc. (90) on Oxygen, -30ft/min ascent.
Off gassing starts at 184.3ft
OTU's this dive: 125
CNS Total: 55.5%
The deco software is copyrighted, but slightly outdated, since it has been superseded by a more recent upgrade. Therefore hopefully the mod squad will not be bothered by the posting of this example.
[Before anyone tries the above, you need to be advanced trimix trained and certified. You can obtain such training from IANTD, TDI, NAUI, etc. Google them for "technical diving."]
boomx5
Contributor
triton94949:
I could be wrong, but I think he got a lot of his stuff from Bill Hamilton and Bruce Wienke. He and JJ then went out and did the dives off of Tables they generated and worked out what worked best. I'll PM Bruce and see if he can help shed some light on his involvment with the WKPP.
Dr. Bruce Weinke advocated staying on the helium all the way up as I recall. There's several threads here on the board wshere we discussed this.
Lots of folks are adding the he to deco gas without adding deco time. I've dumped helium into deco gasses but not enough to do a whole bunch one way or the other and usually on deeper mixes like a 120 ft bottle.
Lots of folks are adding the he to deco gas without adding deco time. I've dumped helium into deco gasses but not enough to do a whole bunch one way or the other and usually on deeper mixes like a 120 ft bottle.
triton94949
Guest
boomx5:
Then I believe it is called hear-say. Shouldn't you instead be quoting Bill Hamilton and Bruce Weinke and citating their written references?
triton94949
Guest
MikeFerrara:
Mike I know people are doing it. I said that people are doing it. I have seen people doing it.
What I have not seen is a major decompression algorithm programmer coming up with a program that gives you less or even the same deco time when you use TMX 50/XX in place of EAN50. All that I have seen is longer deco time requirements with the TMX 50/XX.
And I have read Dr. Weinke's books and deco manuals. Yes they are revolutionary. No they are not mainstream. Yes they are interesting. But some of the concepts are self defeating. Such as planning your second dive to be 30 ft shallower than the first.
Did the shipwreck suddenly get 30 ft shallower? I think not.
And universal 3 hour surface intervals? Surface intervals are a planning issue that vary with the depth and exposure time. They tend to vary between 2 hours to 5 hours. There is nothing magical about 3 hours. If I need to shave off 30 ft from my MOD on Dive 2 because I was limited to 3 hours of surface interval, there is no use in diving Dive 2, since the shipwreck did not get any shallower in the past 3 hours.
How did you like the RGBM manual?
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