Diving to 130 ft ?

[StreetDoctor]

1.45 is greater than 1.4 and the narcosis you encountered would increase your WOB increasing the odds of an O2 hit. If 1.45 is ok then why not 1.6 or 1.7 or greater? Not saying that you were in any real danger, just that based on current standards you could argue that you violated the MOD. I am not the scuba police (doh! don't look at my signature) you can dive to a 3.0 if you like. It's just not what is currently recommended.

If it was a simple dive and you had to stare at your computer to get over your "dark narc" what if something would have arose with your buddy? As simple as an entanglement? I'm just commenting on the dive you described.

 

[fnfalman]

1.45 is greater than 1.4 and the narcosis you encountered would increase your WOB increasing the odds of an O2 hit. If 1.45 is ok then why not 1.6 or 1.7 or greater? Not saying that you were in any real danger, just that based on current standards you could argue that you violated the MOD. I am not the scuba police (doh! don't look at my signature) you can dive to a 3.0 if you like. It's just not what is currently recommended.

If it was a simple dive and you had to stare at your computer to get over your "dark narc" what if something would have arose with your buddy? As simple as an entanglement? I'm just commenting on the dive you described.

So, if I were to dive 30% Nitrox and still get narced out of my mind, then what? I couldn't rescue my buddy or get out of entanglement, now, can I?

That 0.05 difference in ATA somehow make me a "safer" diver if I had stayed at no more than 1.4?

Diving is a risky business. When you do a dive, you take a certain risk. You plan for the worst and hope for the best.

 

[StreetDoctor]

So, if I were to dive 30% Nitrox and still get narced out of my mind, then what? I couldn't rescue my buddy or get out of entanglement, now, can I?

The mix had nothing to do with that, just the fact that you classified it as a very easy dive yet you needed to stare at your computer to assure you had air.

 

[DiveNav]

.....How am I going to get an O2 hit if I don't break maximum operating depth for 32% Nitrox?....

???
MOD is ALSO based on what number you want to use for PPO2 ...

Yes, of course, according to what we know today (see table below), you could stay at 1.5ATA for 2 hours before you get a CNS hit ....

Me?
I really don't know EXACTLY what is going on inside my body ... I just do some research and then I try to figure out how to come back alive

Alberto (aka eDiver)

 

[Scott L]

So, if I were to dive 30% Nitrox and still get narced out of my mind, then what? I couldn't rescue my buddy or get out of entanglement, now, can I?

You are presenting a good case for more training. Advanced nitrox/decompression procedures and prehaps trimix. With the former you can stay within safe limits of O2 exposure while at the same times gain back lost BT with a few minutes of deco as a result of an increased nitrogen pressure. Trimix would obviously mitigate the danger to you of narcosis with along with a much greater ability to manage problems such as an entangled buddy.

 

[Scott L]

The mix had nothing to do with that, just the fact that you classified it as a very easy dive yet you needed to stare at your computer to assure you had air.

Upon further reflection tied to my thoughts offered above I agree with you on all accounts. Have you looked at O2 related deaths amoung DAN's accident reports? I would be interested with the statistics for this catagory and at what exposures divers ran into trouble...

 

[Bonairetrip]

So, if I were to dive 30% Nitrox and still get narced out of my mind, then what? I couldn't rescue my buddy or get out of entanglement, now, can I?

That 0.05 difference in ATA somehow make me a "safer" diver if I had stayed at no more than 1.4?

Diving is a risky business. When you do a dive, you take a certain risk. You plan for the worst and hope for the best.

Last I heard (and the thinking might well have changed since my training), Nitrox has no benefit in terms of reducing narcosis. So, 30 vs 32 is neither here nor there in that regard.

Yes, a .05 difference in the PP02 could make a difference although it seems unlikely in this instance. As others have noted, it depends on what one thinks the safe max PPO2 figure is. I think most agencies say 1.4 with a contingency of 1.6. It is also important to track or total 02 exposure over the diving day.

But yes, for this dive EAN 30 would make you a "safer" diver (assuming you ended at the same or a better point in terms of N2 loading). Using iNitrox with EAN 32, it says you hit 1.4 at 111 ft and 1.6 at 132 ft. At 125 ft (you said 120-something was your depth), you would be at 1.53 (so, 0.13 above the 1.4).

I agree that, in diving, the limits, at least in one sense, appear sort of arbitrary. For example, going one minute above the NDL does not guarantee DCS. Going one minute under the NDL does not mean I cannot get DCS. It is all about risk -- the closer one gets to those lines, the higher the risk. Going above the lines increases the risk further.

I also agree that you should plan for the worst and hope for the best. (In between are many things one can/should do to help increase the odds of a good outcome). To me, planning for the worst (an O2 hit) means I keep my PPO2 at or under 1.4.

 

[fnfalman]

The mix had nothing to do with that, just the fact that you classified it as a very easy dive yet you needed to stare at your computer to assure you had air.

It was an easy dive. No overhead penetration, no heavy current, good viz.

 

[fnfalman]

Trimix would obviously mitigate the danger to you of narcosis with along with a much greater ability to manage problems such as an entangled buddy.

That's slated for next year's training.

 

[Bonairetrip]

According to the PADI table, with 32% Nitrox, at 120-ft, PPO is 1.48 and I can stay up to 19-minutes before hitting NDL. Consider that I was at depth for 10-minutes (planned bottom time), I think that I was OK. Of course, you are welcome to stick to the 1.4 ATA limit.

How am I going to get an O2 hit if I don't break maximum operating depth for 32% Nitrox?

My planned dive was more than sufficient with the table and within the dive computer's plan.

According to my PADI dive tables (if that is what we are quoting), it effectively sets the MOD of EAN 32 at 110 ft by saying depths below that are for contignecy only.

My recollection is also that there are unexplained 02 hits just as there are unexplained DCS hits. In other words, it is a bit like saying how am I going to get bent if I don't break the tables. The answer: it happens.