Diving Hypoxic Diluent on a Normoxic Dive

decoweenie

Just curious...

Why were you using 10/50 diluent in a Normoxic course ?

And used only 1 x 2L tank for the whole Normoxic course ?

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CCR900

I believe the man wrote MOD2.......

decoweenie

Yes, and isn't ?

• mod-2 = Normoxic Trimix
• mod-3 = Hypoxic Trimix

If I misunderstood something obvious, please forgive me...

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"...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..."

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CCR900

Yup sry I was thinking 2nd course of Tx.... Iwill go back to sleep.....

vulcan

OK, I did the course last week so this is new to me. The IANTD course content says: "the Fo2 in the dilluent will provide a Po2 no greater than 1.1"

So 10/50 at 60m provides a Po2 "no greater than 1.1"

As I said, I'm new to trimix, so if I've missed something, I'm sure someone will be along to correct me.

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decoweenie

Told you NEVER to do that again...

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decoweenie

I am not flaming you or anyone, this is just for discussion...

10/50 @ 60m = 0.7 PO2 which is certainly less than 1.1, however, so is fO2 of 15%... 0.15 @ 60m = 1.05

However, IANTD standards say that Normoxic Trimix course must be done up to 60m, so I take as 59m is the limit for discussion sake.

So without going into 3-decimal places, you could actually do the Normoxic course with fO2 = 0.16 (0.16 * 6.9 = 1.104)

I am just a little sensitive about Normoxic student using hypoxic diluent since (if you read one of the threads) 2 weeks ago, we pulled an untrained diver from the water passed out from using hypoxic diluent. He just left the boat less than 1 minute...

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Dutchy

Phi do you for one second beleive that guy wouldn't have had the same problem with a normoxic dil? (e.g. fO2=0.16) I mean for OC the difference is obvious and crucial but on CCR you (or the computer) blend on the spot right? Your title and conclusion back then said it all....

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decoweenie

No, I don't think it would have made a difference in the case there. But that's a different topic, and it wasn't a "controlled" enviroment by anyone but the diver.

I am just wondering why hypoxic diluent was used in a normoxic course here in a controlled environment of a course...

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vulcan

* Note to admin*
I'm conscious we've hijacked someone elses thread here, so if this is more appropriate somewhere else, or in a new thread within the training forum I'm happy for it to be moved.

I need to be careful here....I speak with all of 5 days trimix experience and I feel like I'm sticking my head in the lions mouth. Please understand that what I say is intended to have no arrogance or swagger about it but there may be things I beleive in naivety that may be wrong, or as you hint, dangerous. So in the spirit of discussion and learning I'll stick my neck out.

OK, the diluent was 10/50. Whereas I understand that breathing just this, in the shallows, it would be hypoxic, but on descent the Po2 would increase, so hopefully not a problem. However, it wasn't being breathed on it's own, it was the diluent in a unit that in "standby" keeps the unit at a set point of 0.4. Once in the water it changes set point to 0.7, and as I descend the Po2 will increase. The unit notifies me of a change in Po2 either up or down, by even the smallest ammount both visually and audibly, so if the loop gas is badly out I can respond to correct, hopefully by staying on the loop, but ultimately I can bailout to the 20/20, breathable at all stages of the dive. At the target depth (60m) I change to a set point of 1.2 which obviously the unit maintains.

On ascent, although the Po2 will be falling, the unit is still trying to maintain 1.2, all the way to the shallows. In fact, on the training dives we did we left set point at 1.2 'till we exited the water. If at any time the Po2 fell to a level that was not capable of sustaining life, the unit would (should?) have notified me well in advance so I could prevent this. That doesn't include manually checking the Po2 either. Again there was the bailout if everything failed; The bailout plan was, I understood one of the most important constituents of the course.

So my question is this, at what point is the 10/50 a problem when being used as a diluent on this training dive. I accept you may be sensitive because of the recent experience you had with the student on a hypoxic mix, but the way I understood it, I was never breathing just the diluent at any stage of the dive, and nor should I have been.

I stress that I'm coming at this subject from behind and am still learning, but if Ive missed something, I clearly need to know, and soon.

Regards

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"Blessed are they who learn from their mistakes. For they shall make, if not necessarily fewer of them, different and more interesting ones."

Martin