Diving 32% Nitrox with "Air" Algorithms

[L13]

Yep. I was being mostly facetious. When I first got that computer, I thought for a minute that it might be a good idea, but then I thought harder about it and decided to turn off that option.

Any more, checking my FO2 setting on my computer is part of my predive checklist, it changes often enough.

 

[boulderjohn]

Any more, checking my FO2 setting on my computer is part of my predive checklist, it changes often enough.

Roughly 17 years ago, I read a case of someone who got bent because he made a last minute switch to a tank with air and forgot to switch his computer from 32%. That spurred me to write to PADI and suggest that a very important part of the predive check (BWARF) was missing--the instruments used to track the dive. They replied that it was a great idea and they were working on a new one that included it. They said it should be public soon. I'm still waiting, but I am losing hope.

I changed it myself, adding an I "instruments," which would cover both watches and computers. That was 17 years ago, so maybe I would change it to C for "computer" today. I would have to come up with a new mnemonic, and I should anyway, in light of recent history. I taught my students to use BWRAIF, and remember it as Bruce Willis Ruins Another Independent Film.

 

[NW Dive Dawg]

Roughly 17 years ago, I read a case of someone who got bent because he made a last minute switch to a tank with air and forgot to switch his computer from 32%.

I think most if not all folks here would agree that this stated scenario could very well have that result...

But the question as it relates to this thread would be the reverse..........What would have likely happened if this same diver had made a last minute switch to a 32% tank and forgot to switch his computer from air?..... AND as mentioned in the original post, it was an NDL dive no deeper than 100ft.?

 

[AJ]

But the question as it relates to this thread would be the reverse..........What would have likely happened if this same diver had made a last minute switch to a 32% tank and forgot to switch his computer from air?..... AND as mentioned in the original post, it was an NDL dive no deeper than 100ft.?

What about thinking what you are doing in stead of letting the computer decide for you?

What strikes me most in this thread is how much divers seem to rely on what their computer is telling them. They go up when the computer says so, they won't go deeper when the computer says so and they do a stop when the computer tells them to. But wait, when they lie to the computer, what exactly is that computer telling them? The computer doesn't know better, what about the diver?

Imo, the computer is trusted advisor. Give it all the information it needs to advise, don't lie to it. But always own your dive. The computer is just a dumb piece of electronics that doesn't understand conditions and whats going on except for time, depth and gas mixture.

 

[Blackcrusader]

Roughly 17 years ago, I read a case of someone who got bent because he made a last minute switch to a tank with air and forgot to switch his computer from 32%. That spurred me to write to PADI and suggest that a very important part of the predive check (BWARF) was missing--the instruments used to track the dive. They replied that it was a great idea and they were working on a new one that included it. They said it should be public soon. I'm still waiting, but I am losing hope.

I changed it myself, adding an I "instruments," which would cover both watches and computers. That was 17 years ago, so maybe I would change it to C for "computer" today. I would have to come up with a new mnemonic, and I should anyway, in light of recent history. I taught my students to use BWRAIF, and remember it as Bruce Willis Ruins Another Independent Film.

I have found a few divers with 32% settings they did not change back to 21% on pre dive checks. Most are oops thanks for catching that as DC checks are often uncommon. I do check also to advise what settings my Perdix has to their DC. If they are using a DC with more conservative setting then I tell them pls follow your DC NDL and don't just dive along with me. I have had a few instabuddy's lock out on Sunnto's for exceeding NDL when I have not on my Perdix and they missed that deco obligation.

 

[NW Dive Dawg]

I think most if not all folks here would agree that this stated scenario could very well have that result...

But the question as it relates to this thread would be the reverse..........What would have likely happened if this same diver had made a last minute switch to a 32% tank and forgot to switch his computer from air?..... AND as mentioned in the original post, it was an NDL dive no deeper than 100ft.?

What about thinking what you are doing in stead of letting the computer decide for you?

What strikes me most in this thread is how much divers seem to rely on what their computer is telling them. They go up when the computer says so, they won't go deeper when the computer says so and they do a stop when the computer tells them to. But wait, when they lie to the computer, what exactly is that computer telling them? The computer doesn't know better, what about the diver?

Imo, the computer is trusted advisor. Give it all the information it needs to advise, don't lie to it. But always own your dive. The computer is just a dumb piece of electronics that doesn't understand conditions and whats going on except for time, depth and gas mixture.

We're all agreed both listening to your computer and to yourself is extremely important. My question back to John was simply asking what would have likely happened if the "mistake" had been reversed.

 

[boulderjohn]

We're all agreed both listening to your computer and to yourself is extremely important. My question back to John was simply asking what would have likely happened if the "mistake" had been reversed.

I didn't repond because the answer was obvious. If the mistake had been reversed, the diver would have been accidentally doing what some people have advocated in this thread.

 

[60plus]

I have had a few instabuddy's lock out on Sunnto's for exceeding NDL when I have not on my Perdix and they missed that deco obligation.

Maybe just your wording but Suunto's do not lock out for exceeding NDL (Sunnto's might) A Suunto only locks out if you do not follow the required decompression time that results from exceeding NDL. If decompression not carried out it locks out for 24 hours with aim of advising diver not to dive again during that period to reduce risk of DCS.
For me starting an ascent with 10 minutes of NDL remaining would be a waste of valuable bottom time. Dive times at 30 to 40 m are way too short anyway to waste 10 minutes.

 

[scubadada]

...The Oceanic I used to use did default back to air, so it needed to be set. It also had an option to revert to an impossible mix if you didn't manually start the dive. It would assume 21% O2 for N2 calculations and 50% O2 for MOD/O2 calculations. I disabled that on mine as I thought it was a bad idea...

I had one of those computers that reverted to 50% O2...it was a pain in the a$$. More than once I had to ascend, spend 10 minutes at the surface waiting for the computer to think it was a new dive, reset the computer, and then descend again.

The worst were the computers that reverted to air after 24 hours. A diver would check his computer before a dive, go about other preparations, jump in the water, and then discover at some later point that it had changed before the descent.

My family has many old Oceanic computers, 3 Pro Plus 2s, a VT3, a Geo 2, and a VT4. The nitrox setting reverts to air after 24 hours, a new series of dives. If close in time, it is not difficult to check your FiO2. Nobody in my family has "accidentally" dived on air.

The 50% O2 setting is ridiculous, it can be turned off/on, we've never turned it on, problem solved.

Sometimes people make problems out of the simplest things.

 

[arew+4]

Going all the way back to oceanic data plus, if you accidentally dive on FO2 21 you were stuck with it until you got a 24 hr break. One button navigation was the worst.