Diving 32% Nitrox with "Air" Algorithms

[davehicks]

I know people who set their clocks 10 minutes ahead of the actual time to avoid being late. This is just regressive laziness and a sad attempt to fool yourself out of bad habits. Doing the equivalent on your dive computer is just as backwards and ridiculous. Sorry!

If you want to have a safety buffer then increase the conservatism of you computers algorithm. If you have GF then use something like 30/70. You will have a bigger buffer than if it you tracked to air, and your stats will accurate and actionable.

 

[Cheizz]

I don't think it's wise to alter your measuring device to lie to you. If you want conservatism, use a more conservative setting, and plan shorter or shallower dives. But your computer should give you facts and advice based on those facts.

 

[Divin'Papaw]

As others have said, I want my computers accurately tracking what I'm breathing. If I want more conservatism, I dive more conservatively. For my computers (Shearwaters), that can include setting the GF values more conservatively, monitoring and keeping my SurfGF lower, not ridding or approaching NDL, doing a 5-7 min safety stop, or all of the above. I don't need any "tricks" like diving nitrox with computers set to air in order to dive more conservatively.

 

[L13]

It is safety practice not safety factor ie. dive conservatively.
What is the point for dc came in with GF or whatnot? I am glad I did not waste any money on those.

I'm not sure what your point is.

Are you suggesting that it is good safety practice to lie to your computer? Are you saying computers with GF are a waste of money?

 

[rob.mwpropane]

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?

I think it's a good thing you're thinking outside of the box as opposed to just trusting the little beep beeps on your wrist.

Dive 32%, set for 32%, pad your safety stop, make the ascent from the last ~ 30' very s-l-o-w and you and your wife will be worlds ahead of a lot of divers out there.

If you own a dc that can display surfgf, keep an eye on that and can adjust "on the fly". I think it's pretty widely accepted that ~ 70 is a pretty "conservative" #. Most people feel fine at 80 or even 85.. heck, some recreational dc's closely match 95..

Hope you guys have a blast.. take pictures for the rest of us!

 

[Norwegian Cave Diver]

This seems fundamentally more risky than diving your computer correctly set for your nitrox percentage, and setting conservationism to what ever level of conservationism you want. As you are doing it now, you are lying to your computer, and you are lying to any emergency res ponders that might use the data on your computer to assist you.

If the maximum conservative setting on your computer is not conservative enough, you can just not dive until 0 NDL. Maybe turn the dive at 5 minutes, or 10 minutes left on NDL. This way, you will not be lying to your computer, and your computer will not be lying to you. You will always know your real limit, and will know how conservative you are really being.

Great response.

 

[arew+4]

So my wife, wanted to switch to Nitrox for safety reasons, I did not, "if it ain't broke don't fix it", she want to keep the computer on air, the thinking being 15% less nitrogen = X% less risk all else being equal. The response on the board was much the same as this time. I ended up adjusting her computer to the PZ+ algo and adding +2 or something conservative factor, and EAN32 for the gas. With the settings her NDLs are roughly equivalent to my Air on DSAT numbers. End result she is using EAN as a safety tool not a dive extending tool, (we always end dive because she is getting cold anyway.) and I am continuing to do what has worked for me for the last 30 years.

So from a philosophical standpoint I am in good standing with the don't lie to your computer crowd, who oddly enough have significant Venn overlap with the manipulate the sh!t out of your computer to get the answer you want faction.

Additionally, there are respected diving medicine professionals that advocate diving EAN on air tables/settings. I posted a reference to a DAN Alert Diver article in the other thread. If you were incapacitated while diving the treatment would not be altered much by the gas used they can always look at the tank sample the contents use your computers dive profile to reconstruct your actual gas exposure by correcting the gas when they analyze the data.

 

[inquis]

Easy enough to do using NOAA oxygen exposure tables.

For multi-level dives? No thanks. Computers excel at that sort of tedium.

 

[ChuckP]

I don't believe that lying to your computer gives you any benefit - give the computer the correct info and adjust the conservation factor.

Something about NDL's - your body can have a high N loading while you have a high NDL number. A NDL of 99 only means you are just below the adjusted M value line of whatever conservation factor you have choosen - that is not the best way to understand the physiology of what is actually happening. The NDL number is just telling you how long you can stay at the current depth without entering deco......

OTU's really do not come into play in the recreational diving - even diving 36% repeatadly very aggresivally - you'll tap out on N loading long before OTU's

 

[Blackcrusader]

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?

Yup I have done this and just keep to 30m max depth. Sometimes as dive buddy may also be using 21% sometimes as I am doing shallower dives anyway around 20m max. There is no reason you cannot do this if you are not exceeding your set max depth for 32%. Others have mentioned your O2 loading on the DC not being accurate.

I've done this only when doing say 6 dives over two days. Pretty much on constant 3 to 4 dives a day for 12 days straight I set my DC to what gas I am using.