Reasons NOT to use Enriched Air?

[Thalassamania]

There is no "cliff" that you're going to fall off suddenly. There are times and dives when using EAN36 down to 1.6 or even 1.8 is the thing to do, there are other times and dives when for the same depth EAN32 or air will be a better choice. EANxx is just a tool, but it is doubled edged, and if you're careless it can cut you both ways.

 

[Blackwood]

There is no "cliff" that you're going to fall off suddenly. There are times and dives when using EAN36 down to 1.6 or even 1.8 is the thing to do, there are other times and dives when for the same depth EAN32 or air will be a better choice. EANxx is just a tool, but it is doubled edged, and if you're careless it can cut you both ways.

Sensible posts such as these will be disregarded as a matter of course. It's the scubaboard way

 

[Catt99]

There is no "cliff" that you're going to fall off suddenly. There are times and dives when using EAN36 down to 1.6 or even 1.8 is the thing to do, there are other times and dives when for the same depth EAN32 or air will be a better choice. EANxx is just a tool, but it is doubled edged, and if you're careless it can cut you both ways.

Hi Thal - can you expand on this a little, please? As a novice diver I'm not all that interested in pushing limits on my own susceptibility to to ox tox -- if not a cliff, it certainly feels like a crumbling and steep slope that I should be cautious about trying to peer over. If I knew my planned dive depth would put me at 1.6 or 1.8 on EANx36 I'd be much more inclined to either change my plan or use a less rich mix. When and why would you (or someone) choose to use a mix on a dive that resulted in that pp02 exposure?

 

[SteveAD]

Hi Thal - can you expand on this a little, please? As a novice diver I'm not all that interested in pushing limits on my own susceptibility to to ox tox -- if not a cliff, it certainly feels like a crumbling and steep slope that I should be cautious about trying to peer over. If I knew my planned dive depth would put me at 1.6 or 1.8 on EANx36 I'd be much more inclined to either change my plan or use a less rich mix. When and why would you (or someone) choose to use a mix on a dive that resulted in that pp02 exposure?

The cliff reference goes back to an earlier post about EAN being a bad choice for wall dives with no bottom, where the diver could "fall" below the MOD for their mix. With decent bouyancy control no-one is going to "fall" off the wall.

Earlier posts also referenced the apropriateness of elevated PPPo2 at different times during the dive. A PPo2 of 1.4 during the "active" (don't want to say working or nearass will scold me ) and a PPo2 of 1.6 to 1.8 during a resting deco stop.

 

[Thalassamania]

Actually my cliff comment was intended as an analogy and was not referring to an actual cliff or wall. You are quire right when I comes to deco, but it goes beyond that. If I have an intense diving schedule, in warm clear water, with dives that require very little physical effort (e.g., fish behavior watches) I may well go as high as a _ppO₂ of 1.8 on some parts of some of the dives. But, if I have to do a few dives with heavy work in bad currents, with low visibility I'll hedge my bet and try to keep the _ppO₂ in the range 1.4 (or lower) so that I have some margin. My real point is that rules for an exact _ppO₂ out of the context of the dive(s) I find to be more posturing, or lack of operational knowledge, than anything else. It's like depth ... 130 is ok, but if you hit 131 ... you're a'gonna die!

 

[SteveAD]

Actually my cliff comment was intended as an analogy and was not referring to an actual cliff or wall. You are quire right when I comes to deco, but it goes beyond that. If I have an intense diving schedule, in warm clear water, with dives that require very little physical effort (e.g., fish behavior watches) I may well go as high as a _ppO₂ of 1.8 on some parts of some of the dives. But, if I have to do a few dives with heavy work in bad currents, with low visibility I'll hedge my bet and try to keep the _ppO₂ in the range 1.4 (or lower) so that I have some margin. My real point is that rules for an exact _ppO₂ out of the context of the dive(s) I find to be more posturing, or lack of operational knowledge, than anything else. It's like depth ... 130 is ok, but if you hit 131 ... you're a'gonna die!

OK. My bad.

Disclaimer: My last post, above, was in no way answering for Thal. It was entirely my own answer.:14:

 

[Thalassamania]

Steve, yours was a perfectly reasonable interpretation. I only corrected it because I saw where I'd not been clear. Thanks for pointing it out.

 

[nereas]

No it isn't...

According to who ?! ...

Wrong. It also places them further to the safe side of the curve for immediate acute O2 hits. Something you dont seem to realise even exists.

...

String, you are definitely starting to sound really Irish. And there is something wrong in your cornflakes too.

An NDL diver who does not exceed 1.6 ATAs ppO2 is never, ever going to exceed ox tox limits. It is simply not possible. He/she will get DCS first, long before CNS toxicity. Do the math.

 

[nereas]

...

Earlier posts also referenced the apropriateness of elevated PPPo2 at different times during the dive. A PPo2 of 1.4 during the "active" (don't want to say working or nearass will scold me ) and a PPo2 of 1.6 to 1.8 during a resting deco stop.

DWayne will probably barf now, since somebody mentioned 1.8 ATAs. I am waiting for him to post about it.

As for me, 1.6 ATAs is my own absolute ppO2 limit.

 

[DwayneJ]

As for me, 1.6 ATAs is my own absolute ppO2 limit.

Did you go back and edit your posts to be sure you did not contradict yourself?