Deco gases

[Mark Chase]

Originally Posted by [b

Quote[/b] (Bob Cooper @ Dec. 24 2003,18:14)]Mark

I only saw your reply after posting mine......

40mins at 65m is too long for an ocean dive.  The run time would be around 2 hours.  As you know this is a little too long for us, and the bottom gas reserves are a little marginal with 2x15L and dangerously marginal with 2x12L.  I'll be doing some more of this sort of diving next year and I've just invested in a pair of 15's.

Keeping the bottom time to <30mins at 65m would give ample reserves of deco gas.  And we still have the drop bottle of 100% to fall back on if we loose that for some reason.

Happy Xmas!

Bob

Fair enough but even cutting the bottom time down to 25mins you would still need 240bar in a 10ltr to get out on the 50% and you would need 270 bar in a 10 if using 35% and ignoring the He in the deco mix.

As we both agree a drop tank is the answer in this range

Happy Xmas to you too, hope to see you in the new year.


ATB

Mark Chase

[And]

Originally Posted by [b

Quote[/b] (Mark Chase @ Dec. 24 2003,18:29)]As we both agree a drop tank is the answer in this range

Happy Xmas to you too, hope to see you in the new year.


ATB

Mark Chase

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Originally Posted by [b

Quote[/b] (Bob Cooper @ Dec. 24 2003,18:14)]Mark

And we still have the drop bottle of 100% to fall back on if we loose that for some reason.

Happy Xmas!

Bob

Hi

Actually, I don't think thats what Bob said at all. The drop tank is in case you lose your 50% bottle. If you need O2 for the deco, you take it with you.

Happy New Year

Andy

[Mark Chase]

Originally Posted by [b

Quote[/b] (wetlettuce @ Dec. 27 2003,11:33)]

Hi

Actually, I don't think thats what Bob said at all. The drop tank is in case you lose your 50% bottle. If you need O2 for the deco, you take it with you.

Happy New Year

Andy

No M8 we were discussing loosing your rich deco mix during the dive. The diver said he planned to bail out and finish deco on his 50% or 32/35 and I was pointing out that this was impracticle on deep 60+ dives

ATB

Mark Chase

[Bob Cooper]

Not sure where the misunderstnding is here......I've lost the plot a bit on this one too.

What I meant was, for 65m for 30mins you would carry two deco gasses, 50% and 100%. &nbsp;You can do the deco on either one or the other, or preferably both! &nbsp;If you loose the 50% bottle (by &quot;loose&quot; I mean it doesn't work for some reason, not that you physically &quot;loose&quot; it i.e. that you remove it and then can't find it again) you can use another team members 50% bottle when he has finished with it, then you both move up to your next switch at 6m. &nbsp;If you get to the 6m gas switch and find that your 100% bottle doesn't function for some reason, you can send up a yellow and the boat will send down a 100% bottle.

Same rules apply for cave diving as wreck diving. &nbsp;The only difference there is that you CAN actually &quot;loose&quot; your deco gas in a cave!

Happy New Year!

Bob

[Mark Chase]

No I was with you all the way. A two deco gas dive and gas lost due to valve failure or similar not lost lost

I can see how having your buddies left over 50% can extend yore available gas but you know me Bob I love my independance

ATB

Mark Chase

[wreck hunter]

Hi guys .

can someone explain to me the benefits of using Helium in  deco mixes. I never came across this in my trimix course, but many of you mention it as a matter of fact here and even in other DIR websites ! I thought that the reason for using helium is to reduce the narcotic effect what benefit can it possibly have in 6 mtrs to 30 meter range?

[Mark Chase]

Originally Posted by [b

Quote[/b] (wreck hunter @ Jan. 01 2004,19:02)]Hi guys .

can someone explain to me the benefits of using Helium in  deco mixes. I never came across this in my trimix course, but many of you mention it as a matter of fact here and even in other DIR websites ! I thought that the reason for using helium is to reduce the narcotic effect what benefit can it possibly have in 6 mtrs to 30 meter range?

Helium is a faster gas in that it on gases fast and off gases fast. Some would disagree and argue that it on gases fast but gets fixed and off gases slowley. The DIR reserch discounts the later theory and maximises the claimed fast off gassing benifits of the He to reduce deco. They also use the He to reduce shalow depth narcosis to prevent task loading related deco accidents.

atb

Mark chase

[Simon Ciantar]

Originally Posted by Bob Cooper

Yes, one of the reasons for using helium at 36m is the reduced narcotic effect and because it is a &quot;faster&quot; gas. &nbsp;Other reasons include the reduced breathing effort due to reduced gas density leading to reduced CO2 retention. &nbsp;Reducing breathing effort and CO2 retention are thought to reduce susceptibilty to Oxygen toxicity too.

Just using 35% nitrox at 36m would be of little benefit.

But I thaught that one should get off Helium as quickly as possible when coming up , I do dives to 60-65mtrs regularly (though usually bottom gas is air so far) and i switch to travel gas at about 30mtrs ( EAN 32- 36%) then to deco at about 15mtrs ( EAN 60- 70 %)

Does the intriduction of Hel in the travel gas reduce eventual deco time ?


Appreciate your comments as this subject has been a question mark for me for some time

[Phil Ennis]

Originally Posted by Simon Ciantar

But I thaught that one should get off Helium as quickly as possible when coming up , I do dives to 60-65mtrs regularly (though usually bottom gas is air so far) and i switch to travel gas at about 30mtrs ( EAN 32- 36%) then to deco at about 15mtrs ( EAN 60- 70 %)

Does the intriduction of Hel in the travel gas reduce eventual deco time ?


Appreciate your comments as this subject has been a question mark for me for some time

Hi Simon, I would do some digging in the archives, this one and others have been covered quite comprehensively and makes some very interesting reading. Have a good search round and I look forward to you adding your 2p.

[Simon Ciantar]

Originally Posted by Phil Ennis

Hi Simon, I would do some digging in the archives, this one and others have been covered quite comprehensively and makes some very interesting reading. Have a good search round and I look forward to you adding your 2p.

Would like to Phil maybe you can point me in the right direction im still finding my way in this site