Oxygen Toxicity risk with Nitrox?

[DiveProKoko]

I'll add that we were told by the guide to not go below 40 meters, but 35 to 40 is okay.
All the dives were guided, unless one (two) chose to go without a guide.

As a dive pro, I'm a little concerned that a DM, who knows he has Nitrox divers in his/her group, would set a depth limit exceeding the MOD for those divers without at least remidning them of it. I'm a total advocate for self-reliance and the "you're responsible for your dive plan and your buddy" attitude, but from a professional standpoint it's not good practice. If you're not going to "guide" the group (which IMHO includes more than just pointing out neat stuff) why have a guide at all?

 

[BlueTrin]

I’ll be honest: I am a bit concerned that you bend the rules because others do.

Normally people say 1.4 PPO2 for the active portion of the dive because statistically very few people will have an issue with this threshold. And people use 1.6 for deco because you are not finning or moving during deco.

This does not contains statistics but is easy to read:

Oxygen Toxicity

Oxygen toxicity happens with partial pressures overwhelm the body. Severe cases of oxygen toxicity could cause cell damage or other symptoms.

dan.org

 

[Marie13]

Thank you.
My computer does not contain this information.

I'll add that we were told by the guide to not go below 40 meters, but 35 to 40 is okay.
All the dives were guided, unless one (two) chose to go without a guide.

Think for yourself. Don’t let the dive guide or buddies think for you.

 

[rob.mwpropane]

@Lriemann was there any other mix available? Could you request 27%? To me it would make more sense to dive a cooler mix and do a few min of deco, but I've never been on a LOB. I don't know the "rules".

 

[AJ]

Think for yourself. Don’t let the dive guide or buddies think for you.

Agree, that concerns me more than a slightly higher PPO2.

 

[Lriemann]

@Lriemann was there any other mix available? Could you request 27%? To me it would make more sense to dive a cooler mix and do a few min of deco, but I've never been on a LOB. I don't know the "rules".

No other mix.
I didn't think about asking for a lower mix.
I was the least experienced diver onboard with 80 dives.
Most people had 300 or more, and 3 had a thousand.

 

[tursiops]

@Lriemann was there any other mix available? Could you request 27%? To me it would make more sense to dive a cooler mix and do a few min of deco, but I've never been on a LOB. I don't know the "rules".

On most liveaboards, going into deco will keep you out of the water for a day or two. Better to not exceed your MOD, and to not exceed your NDL.

 

[rob.mwpropane]

No other mix.
I didn't think about asking for a lower mix.
I was the least experienced diver onboard with 80 dives.
Most people had 300 or more, and 3 had a thousand.

If I'm being really honest, I think we've all been there. It's a turning point in your diving where you're gaining experience and knowledge but just don't know enough yet (I really don't either, always learning something). So you ask yourself and others questions later and gain more of both for next time.

We have all done "trust me dives" without thinking for ourselves at one point.... I know I have.

On most liveaboards, going into deco will keep you out of the water for a day or two. Better to not exceed your MOD, and not to exceed your NDL.

Well that stinks. It amazes me that they're ok diving a mix that's too hot and beyond rec limits, but not ok doing a hair bit of deco with something better suited for the dive?

 

[tursiops]

Well that stinks. It amazes me that they're ok diving a mix that's too hot beyond rec limits, but not ok doing a hair bit of deco with something better suited for the dive?

I have no idea who that operator was or what their procedures were. They were sloppy/dangerous about mix and depth; they could also be sloppy about going into deco. We do not know.

My point is that suggesting you dive a lighter nitrox is good, but suggesting you go into deco is probably not good. Just accept less NDL. Or, don't dive so deep.

 

[johndiver999]

I think going to 1.6 for a few minutes is not a big deal. However, if you are diving with no bottom and no good reference, dropping down to that sort of depth really becomes dangerous because it can be VERY easy to drop ANOTHER 20-30 feet or so due to a distraction or even a small problem.

I think diving a hard bottom to 1.6 is much different as a practical matter. If I were doing blue water dives with no bottom and pushing the depth limits, I think I would want a float on the surface and a weighted line with something hanging that is very hard to ignore, in other words, provide a good reference. I suppose computer alarms might help too, but I would rather not hope I hear something when excited and buzzed.