Diving 32% Nitrox with "Air" Algorithms

[Belzelbub]

This a recreational scuba site, diving is supposed to be fun. There are risks and you must decide how to mitigate them. Do what works for you, but accept the consequences. Provided you pay attention to the MOD of the Nitrox blend and you are using 32 or less you will have a very hard time raising your O2 sat to anything approaching dangerous.

Technically correct. The mitigation of risks is up to the diver.

If you are diving an old computer with no means to adjust conservatism, then you have less mitigation paths open to you for adding a safety buffer. In that case, diving Nitrox while set to air might make sense. Another option is to move the minimum NDL up from 5 to 10 minutes, or 10 to 15 minutes, etc.

However, if you have a newer computer, chances are you have more options available to you. The manufacturer of the computer (at least a recent model) included the ability to adjust the gas mix. They included that presumably because they intend for the diver to set the computer to the gas they are using. This computer manufacturer also included some sort of adjustment to conservatism factors. They included these as well so that the diver can choose the level of conservatism.

I don't understand the reluctance to use the correct gas mix. If someone has invested in the time and money to get an EAN cert, then presumably they want to dive with EAN. If they also have a computer that allows for adjusting the gas mix and conservatism settings, then why not use them?

 

[Cheizz]

The extent of most dive plans is, if there is a current swim into it on the way out be back on the boat with 500 psi. Try not to go deeper than X.

Even this is a dive plan in my book. If you ignore your 500 PSI alarm or your NDL -/- 10 minutes alarm because of a distraction, you're risking stuff. The dive plan doesn't need to be complicated in order to be called a dive plan.

 

[captboob]

In the interest of adding "conservatism" to our diving, my wife and I when diving the tropics (mostly shore diving on Bonaire ) dive 32% Nitrox. But to increase safety, we still keep our computers set to Air. We fully understand and adhere to the 111ft MOD for 32% and we even augment that by agreeing to stay inside of 100ft max depth as a rule. We just keep our computers set to AIR to add in some more "conservatism" . We then plan and dive the AIR algorithms ....... and NEVER go below the MOD for 32% Nitrox.

Anyone else do this........or does anyone have a reason why not to do this?

Buy a computer, enter your mix and don’t play games with ox tox
If you can’t afford a computer or are unable to plan your gas recipe off a plastic card and a timing device, stay home.

 

[tursiops]

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.

Nor is it guaranteed to be safe from O2 toxicity/CNS issues.

 

[arew+4]

Nor is it guaranteed to be safe from O2 toxicity/CNS issues.

Duh! That is why I said it is an unacceptable level of risk in all caps.

Captain redundant.

 

[tursiops]

Duh! That is why I said it is an unacceptable level of risk in all caps.

Captain redundant.

Just following your lead....of saying things that are well-known to anyone trained to dive Nitrox (which you say you are not)....but we are in Basic Scuba where clarity is essential and you cannot assume the readers are Nitrox trained.

 

[L13]

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.

"UNACCEPTABLE LEVEL OF RISK" and " not guaranteed to cause O2 toxicity or cns symptoms" were my points. What were yours?

Not every agency has a rec limit of 130'. Not all EAN is 32%. Not everything that you can usually get away with is a good idea.

Using EAN with your computer set to air while staying shallower than your MOD is safe. But, with any modern computer, it isn't the safest or best way to add margin to your the NDL limit. If multiple good options are presented to you, why would you pick the less good option?

 

[L13]

Just following your lead....of saying things that are well-known to anyone trained to dive Nitrox (which you say you are not)....but we are in Basic Scuba where clarity is essential and you cannot assume the readers are Nitrox trained.

It is ironic that @arew+4 admits to being untrained in Nitrox, and still thinks his opinion on proper use of nitrox is authoritative.

Even his wife (who is trained) knows not to do it the way he suggests.

 

[MaxBottomtime]

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.

 

[rjack321]

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