Nitrox question

[wedivebc]

PADI allows you to go to 1.6 as a "contingency", whatever that means, so I'd imagine planning to go to 1.6 for short periods is probably fine (so long as you don't need further "contingencies" from there). Where the statement would become dangerous, in my newbie opinion, is if you followed its logic to think it was safe to plan even higher PPO2s for short periods, thinking you don't actually hit that PP02 until you've been at depth for a certain period.

I think contingency here means a milder form of emergency, like "ooops, dropped my camera, Ill just pop down to 130' to get it"

 

[Otter]

bULLs**t What evidence thereis is that Oxygen IS LESS NARCOTIC than Nitrogen at exposures NORMALLY seen by divers. The therory most are using is for INERT GASES!!(your link later on at least states the mechanism is different than other gases).. Oxygen is not inert, its used heavily by the body and there is little increase at the cellular level (the narrcotic theory is based on lipid solubility)..

Most are willinng to accept at high exposure level it is probably somewhat narcotic (not enough study has been done) but at those exposures you would be convulsing (working hard), (or dead - very high exposures) anyway.. The study you quted is the lowest exposure I have seen but ts still above the normal exposure levels.. I'dlike to see how they quantified a 10% reduction in mental ability.. Also the study does nothing to see what various oxyegn fractions (other than strictly po2).. its still to narrow a test to say that oxygen is narcotic.

If you followed the therory (but improper use since its an INERT gas theory)oxygen would be at least twice as narcotic as nitrogen that means anyone doing a hyperbaric treatment (normally 2.8 atas) on 100% oxygen would be blasted, this simply is not the case.. The people are clear headed, if there is a reduction its imperceptable (I amwilling to acceptthe fact that the one study see might have measured some small change)..

I HAVE played games with different mixes, and I know on my body I can see a difference with even a few percent.. I couple of years back I did some test on a 150ft dive, I had 26% in one tank and Air in another (as sling bottles), by buddy would randomly give me a tank and I would have to ID it air or 26%, I was able to ID thes tank 100% of the time, it was really easy when the "switch" was an atual mix switch..

If a real detailed study is ever done it will probably show that in the range commonly used by divers there is a reduction of overally narcosis due to reducing the stronger inert gases (one gas being less narcotic than the other) and that at higher exposures it will have some narcopotency..

Even Helium which people say is not narcotic starts to act narcotic at high exposures as documented and tagught by COMEX to saturation divers..

I actually decended on 26% that I had on my back tanks.. I was unsure how the tests were going to run.. The first tank my buddy gave me was air and I knew it immediately..

Despite previous comments that my statement about O2 being as narcotic as N2 were made with "conviction" the truth is that I have not personally attempted to quantify any level of impairment (N2 or O2) nor have I attempted to even prove it empirically by taking multiple gasses down to depth to 'compare' the different level of impairment with different mixes. I have read much the same material that you all have read/quoted earlier.

So, I will for the record change my comment to read "..there is a view, held by some but clearly not the entire diving community, that oxygen contains certain narcotic properties that some have suggested cause a level of narcosis approaching/equal to/exceeding nitrogen."

 

[Firebrand]

If anyone has seen the NOAA diving manual, they say that a PPO2 of 1.6 ATM will not produce a toxic effect.* However, for the general recreational diving community, the limit is set at a PPO2 of 1.4 to ensure there is a safety margin to allow for those "contingencies."

* NOAA states the PPO2 limit of 1.6 ATM is for their scientific divers specifically trained for that exposure, and anyone else should stick to a limit of 1.4 ATM.

 

[lamont]

All I know is that I was on a dive a week ago where we were on EAN32 dropping down along a wall and I noticed perceptable narcosis. I looked at my depth gauge and we had just dropped down to 85 fsw, which is where I usually start feeling narcosis on air. That's not a double-blind placebo controlled study, but the onset of symptoms were what prompted me to check my gauge and I hadn't been expecting narcosis since I had been expecting the dive to be above 80 fsw. Stuff like that convinces me that EAN is narcotic. Maybe its less and maybe you can tell the difference, but I'd really like to try some 30/30 at those depths and see how a little helium compares.

 

[lamont]

There is an agency that has subsribes to a standard of only using 32% to 100' and above. Deeper than that you should use trimix. Not being trimix certified - at this point that is not an option.

Technically, all you need is a mixing whip, a T of helium and a dream...

I really need to get my butt into a rec triox class at least, because I'm getting sorely tempted to exceed my training...

 

[PhinDiver]

thanks otter, i plan on having my 80s o2 cleaned but have a trip for thursday and they are already filled and im picking up the 120 on tuesday filled to ean32.
what is the going rate to have tanks 02 cleaned i assume this also covers the yearly vip

Depends on the LDC that you go to. Mine charges $35 for the cleaning which does not include the VIP.

 

[PhinDiver]

Can someone explain to me why you need "special tanks" for nitrox if it is still the same gas inside with just a higher oxygen concentration.... That and why would you need to get a tank O2 cleaned to switch it to nitrox? Thanks!

Because the same gas does not go into the tanks. Depending on the method used to mix the fill pure oxygen would be pumped into the tank first. Oxygen does not like hydrocarbons, oil, and could lead to a fire or explosion.