Diving Hypoxic Diluent on a Normoxic Dive

vulcan

Dave, accepted, it does. But if we accept the definition that normoxic is 21%, the depth the course certifies you to at 60m and allows you to dive to on the course takes it to 1.47ATA. The same standards say this should be no higher than 1.1ATA. Using a normoxic mix allows a maximum depth of 42m using the 1.1 ATM benchmark, nearly 20m short of what the course is training to take you to. I just took it that to acheive the 60m in training the mix Fo2 was dropped, but it still fitted the 1.1ATA standard.

Is it just a contradiction in the standards we're splitting hairs about here or am I just confused beyond comprehension

All this debate 'cause a guy asked how much gas costs would be on his Mod 2

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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

Mike

Nah Andy - you just breath too much :-)

I've regularly seen spikes to 1.8 ish on fast decents to 40 to 60m range.
O2 injection volumes per unit time on the Prism won't go as high as it does on the Inspo though. The Prism does take noticibly longer to come up to setpoint than an Inspo.

Besides that, all the other guys have done the PV=nRT thing, you're imagining it
Or possibly you're just a bit more anal about it on a dive where you need hypoxic dil? Or have a faster ascent rate between stops or...

Mike

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dave t

Martin it is confusing, I think when they say normoxic they mean breathable at the surface which is arguably 16%o2 which will just about fit the bill. The older standards used to be much more clear on what gas you could and couldnt use, dont know why they changed it.
I think the point is if you use 10/50 as a dil on a normoxic course then where is the line drawn between normoxic and full trimix!!!??

hth

Dave

vulcan

Aint that the truth!!!

Especially as, to quote clivethediver2, his normoxix trimix cert actually says diluent of 16% o2.

I understood normoxic had to have 21% and anything less than 21% was hypoxic.

Ho hum.......

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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

decoweenie

... I always take it that hypoxic is less than 16% though.

IMHO, my own personal definition of hypoxic gas is you pass out on surface breathing it while not exerting...

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vulcan

Hah!! You again...it was you that got me in to all this mess in the first place!!!!

Your definition of hypoxic sounds reasonable and eminently sensible, but my course laboured the fact that <21% = hypoxic.

In an effort to prove myself right I even did an internet dictionary search on the definition of hypoxic and normoxic....how sad is that!!!

Anyway, until my card comes through, this is all hot air, I'll definitely be on a normoxic dil this weekend

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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

decoweenie

You will thank me later... someday...

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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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silent running

Hi Mike, yeah, you guys are right I must have been imagining it. Asked my Prism buddy again and he confirmed what you all said, he misunderstood me the first time. I was probably imagining it due to nerves on those first hypoxic dives... Sorry for all the wind.

So you noticed the differences in injection btw the Inspo and the Prism too? I knew I wasn't imagining that. The possibility of a big spike was what caused my Inspo dive buddy to choose a slightly leaner tmix for a dive, so he could flush with the lean dil to bring the PO2 down quickly at the bottom, something I had not thought of and not had to deal with on the Prism thus far.-Andy

jradomski

for the inspiration there are 2 types of po2 spikeing..

real and preceived.. There will be a small spike after o2 injection since the injection point is near the sensors.. This could be ignored, as long as the reading returns to normal after a breath.. You wount see this as much on a prism because the injection point is before the stack.. This injection pt (near the sensors) works well for divers who don't breathe quickly.. Divers who have long natural pauses in their breathing patterns would cause extra oxygen additions (or require a longer "off" time in the controller) if the sensors were located farther away from the sensors (like before the stack).

real spikes are caused by excessive oxygen injection,.. the o2 injection on the inspiration is not depth adaptive, so it is possible to get true spikes on deep dives.. This problem can usually be avoided (or lessened - depends on depth) with the correct IP on the oxygen regulator.. Large spikes indicate an IP set too high..

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decoweenie

Isn't that done on one of the recent Vision upgrades ?

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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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