Diving 32% Nitrox with "Air" Algorithms

[L13]

For at least the last decade DAN has been suggesting using nitrox with air tables as a way to increase conservatism. It's fine and both CNS and pulmonary toxicity is basically a non-issue in non-deco nitrox diving.

This is true.

With modern computers you are probably better served to just reduce your GFhigh or bump up your conservatism setting.

But this is the point that I and many others are trying to emphasize (and others are trying to discount).

 

[arew+4]

Although she believes it is safer, which technically it is not. The incidence rate of DCS is .03% or 3 cases per 10,000 dives. Using nitrox can't lower the risk enough to consider it safer than air.

No she does not believe that diving Nitrox is any safer if she were to push the limits, she's not a moron.

 

[tursiops]

For at least the last decade DAN has been suggesting using nitrox with air tables as a way to increase conservatism. It's fine and both CNS and pulmonary toxicity is basically a non-issue in non-deco nitrox diving. With modern computers you are probably better served to just reduce your GFhigh or bump up your conservatism setting. But either way there's 20 pages of drama here over nothing lol

"Given the role nitrogen plays in certain concerns for divers, including nitrogen narcosis and decompression sickness (DCS), it’s easy to see why reducing one’s exposure to it might be appealing. By reducing the amount of nitrogen in the breathing gas and replacing it with a gas the body metabolizes anyway, nitrox can lower the risk of DCS or even safely extend a diver’s bottom time, but it’s important to realize both cannot be done at the same time.

The decreased risk of DCS comes from a fairly simple concept: By reducing the amount of nitrogen in the gas mix, the diver absorbs less nitrogen into his tissues. Compared to the risk the diver would face diving the same profile on air, DCS risk is lower using nitrox, though the risk is not eliminated completely. To take advantage of the increased safety margin, divers can simply plan a dive as though using air and execute the dive using nitrox, though the MOD of the actual gas mix used must be observed."

Nitrox

Nitrox, or enriched air, is a valuable tool for recreational divers. Use of nitrox can lower the risk of decompression sickness. Read more about nitrox.

dan.org

That advice from DAN USA to set your computers on air while using Nitrox was published in 2011. As far as I know, DAN Europe does NOT recommend the practice. Also, all modern computers allow the easy setting of conservatism on your dive computers without resorting to hacks like setting it on a gas you are not breathing.

 

[arew+4]

This is true.


But this is the point that I and many others are trying to emphasize (and others are trying to discount).

Nobody is discounting it. All I'm saying is that by changing settings on your computer you are in essence accomplishing the same thing as leaving them on air and obeying your computer.

 

[arew+4]

No she does not believe that diving Nitrox is any safer if she were to push the limits, she's not a moron.

And as I have already stated we have adjusted her computers algo and con-factor so it generates similar NDLs to my computer same (model different algo and con-factor). So even though her computer says she is diving 32% her NDLs are closer to air and she is accumulating roughly 14% less nitrogen on a given dive.

 

[boulderjohn]

Even if you went to rec limit of 130' on EAN 32, your max ppo2 would be just under 1.6 WHILE THIS IS AN UNACCEPTABLE LEVEL OF RISK, it is not guaranteed to cause O2 toxicity or cns symptoms.

The PADI EANx 32 tables give a maximum bottom time of 18 minutes for a dive to 130 feet. Why, then, is it an unacceptable risk?

 

[Cheizz]

EANx 32 has a MOD of 33.8 m @ PPO2 of 1.4. 130 feet is about 40m right? That would create a PPO2 of 1.6. There's a risk...

 

[Angelo Farina]

Although she believes it is safer, which technically it is not. The incidence rate of DCS is .03% or 3 cases per 10,000 dives. Using nitrox can't lower the risk enough to consider it safer than air.

Correct.
Divig Nitrox for a diving profile which is far from NDL even if done with air has a negligible benefit on reducing risk of DCS, while introducing or increasing some other risks which were negligible with air.
I see the great benefit of Nitrox for some specific dive profiles (long or repetitive dives around 30-35 meters depths).
But I do not see the point of using it for a short single dive at less than 20m.

 

[arew+4]

Correct.
Divig Nitrox for a diving profile which is far from NDL even if done with air has a negligible benefit on reducing risk of DCS, while introducing or increasing some other risks which were negligible with air.
I see the great benefit of Nitrox for some specific dive profiles (long or repetitive dives around 30-35 meters depths).
But I do not see the point of using it for a short single dive at less than 20m.

What are these new and or increased risks you speak of in shallow less than say 30M Dives?

 

[MaxBottomtime]

No she does not believe that diving Nitrox is any safer if she were to push the limits, she's not a moron.

Personally, my wife dives EAN, set to the proper percentage, but with her algo and conservatism dialed up so she's a pretty good match to me on air with clean computers. We still dive the shorter NDL. She wants the additional margin of safety