My DCS Concern

[dytis-sm]

Glad to hear everything is fine!

As a new diver I am surprised how common these incidents are. I recently sold a spare 40cf pony tank to someone who was just recovering from a DCS hit and planned to use the 40cf pony filled with 40% Nitrox for all his future safety stops. I am sure the extra oxygen helps "off gassing" but this is where I think you are getting "technical" and you are better off training for doubles and deco stops ;-)

 

[peterbj7]

You certainly shouldn't be using any nitrox, still less 40%, until you know how to use it and what considerations there are. It's not rocket science but you do need to know and understand it.

 

[boulderjohn]

Glad to hear everything is fine!

As a new diver I am surprised how common these incidents are. I recently sold a spare 40cf pony tank to someone who was just recovering from a DCS hit and planned to use the 40cf pony filled with 40% Nitrox for all his future safety stops. I am sure the extra oxygen helps "off gassing" but this is where I think you are getting "technical" and you are better off training for doubles and deco stops ;-)

The benefit to using 40% is not the presence of extra oxygen. The benefit is the lower amount of nitrogen. If there is a bigger difference (gradient) between the amount of nitrogen in the tissues and amount of nitrogen in what you are breathing, then the nitrogen will come out faster. The extra oxygen is in nitrox because it is the cheapest and easiest way to get less nitrogen.

 

[HIGHwing]

The benefit to using 40% is not the presence of extra oxygen. The benefit is the lower amount of nitrogen. If there is a bigger difference (gradient) between the amount of nitrogen in the tissues and amount of nitrogen in what you are breathing, then the nitrogen will come out faster. The extra oxygen is in nitrox because it is the cheapest and easiest way to get less nitrogen.

Now we're tracking...

 

[Kevrumbo]

I'm going to jump out on a limb here and speculate the OP doesn't have a card/training which allows O2.

Of course not! If OP did have such training, then it goes against all knowledge of Decompression Theory & Practice gained by performing that particular sequence of aggressive N2 stressful air dives -obviously!

 

[dytis-sm]

The benefit to using 40% is not the presence of extra oxygen. The benefit is the lower amount of nitrogen. If there is a bigger difference (gradient) between the amount of nitrogen in the tissues and amount of nitrogen in what you are breathing, then the nitrogen will come out faster. The extra oxygen is in nitrox because it is the cheapest and easiest way to get less nitrogen.

This is where we are getting technical (and thank you for the clarification) something that I am not, so I do not dive the profiles mentioned here ;-) Not trained for those yet...

 

[boulderjohn]

This is where we are getting technical (and thank you for the clarification) something that I am not, so I do not dive the profiles mentioned here ;-) Not trained for those yet...

It really isn't technical at all. PADI let's you use nitrox (with appropriate explanation) on the 4th dive of your OW certification--you don't even need to be OW certified to use nitrox for the first time. You can be nitrox certified the day after you are OW certified.

 

[tamas970]

A short nitrox course will do the job. Nitrox in the pony is gas switching - which is I know, tec territory. However, pony is for emergency use and I would definitely not ban any kind of (<40%) nitrox fill in it, even if the owner is a novice OW with no nitrox cert.

If you switch to pony at (60-120') depth, you immediately start ascending -> no time to take an O2 hit/accumulate significant amount of CNS oxygen. At this point, EANx has only advantages, no disadvantage.

To the OP: I know, this wasn't a square dive, but if it was, dive #2 alone is beyond NDL... Are these bottom times or total dive times? (11min seems to be quite short for total dive time...). Anyway, for 3 or more dives a day nitrox is a must.

You certainly shouldn't be using any nitrox, still less 40%, until you know how to use it and what considerations there are. It's not rocket science but you do need to know and understand it.

 

[DandyDon]

You were getting a bit greedy on dive two. I would put down your mouse and call DAN at 919-684-9111 without hesitation.

Try reading the entire discussion.

 

[uncfnp]

Try reading the entire discussion.

I think he was trying to quote HIGHwing...?