Air backup for a nitrox dive?

[vanderschmooz]

If you were properly trained for nitrox, or trained at all you probably shouldn’t be asking this question. And that’s not being rude, it’s just reality. Put simply, with increased O2 you cannot go down as far.

You're making an incorrect assumption, being that I do know that more O2 limits your depth. I asked this question because I was pretty confused as to why Spare Air sells nitrox versions. Maybe you're past it, but I'm not yet at the stage of experience where I can assume that I know everything.

 

[vanderschmooz]

I hope you haven’t bought the spare air. Get a pony.

They sell Nitrox versions of Spare Air? Wow.

I haven't. Yes, my thoughts too...

 

[caruso]

You're making an incorrect assumption, being that I do know that more O2 limits your depth.

You're making the same mistake @EireDiver606 did.

Within recreational limits, breathing Nitrox at or below 40% does not limit your depth for all practical purposes. Regardless of what sort of tank you're breathing from. Nitrox may only limit your time at certain depths. When you're referring to a Spare Air only, within recreational limits, Nitrox has no practical connection to depth whatsoever.

 

[jlcnuke]

You're making the same mistake @EireDiver606 did.

Within recreational limits, breathing Nitrox at or below 40% does not limit your depth for all practical purposes. Regardless of what sort of tank you're breathing from. Nitrox may only limit your time at certain depths. When you're referring to a Spare Air only, within recreational limits, Nitrox has no practical connection to depth whatsoever.

lol...smh

Based on your academic and medical research, just how long do I have to breath 40% O2 at 130 ft before it becomes unsafe? Can you send me the research paper you did to come up with that conclusion?

 

[caruso]

just how long do I have to breath 40% O2 at 130 ft before it becomes unsafe? Can you send me the research paper you did to come up with that conclusion?

No. Best I can do is direct you towards the Nitrox tables that show a 45 minute limit at 113' with EAN36. Another poster suggested something around 2 minutes.

 

[Lorenzoid]

I haven't....

It might be enlightening if you did a search on this site for "Spare Air," as the utility of this product for various kinds of diving has been debated to death--there are many threads, going back years and years.

The Nitrox angle is a new one to me, though.

 

[The Chairman]

I find no compelling reason to fill any bail out bottle with NitrOx in the first place. What possible benefit could be realized with NitrOx in a bailout? None, nada and squat in precisely that order. Air is all you need. While some of the speculation is based on a quick ascent to the surface, except for a lack of attention, many of the reasons you need extra air may require a bit of time to resolve. I'm thinking specifically of an entanglement scenario.

There is simply no excuse for simply running out of air. That's a failure of both the diver and his buddy. Buddies need to know their partners air supply and relative SAC in order to be a buddy. If simply forgetting to check your SPG is not a possibility, then the air is for other issues, such as the entanglement I mentioned.

 

[jlcnuke]

No. Best I can do is direct you towards the Nitrox tables that show a 45 minute limit at 113' with EAN36.

Well, here's some data beyond that. The points are the data they've used to come up with those limits. If you look at how the data is trending, you'll notice that the line would extrapolate to about 0 minutes around 1.7 partial pressure of Oxygen. Since 40% would give a ppO2 of 2.0 at 130 ft, that suggests to me that it would be exceptionally dangerous to risk such an attempt. Which is probably why no organization or training I'm aware of advises even considering breathing such a mix. If there's other data that says it "might' be okay for short periods of time then I'd love to read up on that though. Barring that, I'd rather we weren't implying that it would "Be fine" because the tables give us a lot of time when we stay within their limits.

 

[caruso]

Well, here's some data beyond that. The points are the data they've used to come up with those limits. If you look at how the data is trending, you'll notice that the line would extrapolate to about 0 minutes around 1.7 partial pressure of Oxygen.

It certainly will not "extrapolate to zero". There is no way to know where that line is going to end up- there's no data. Even given your rather basic 18 year old graph that really says nothing about what happens after the P02 level of 1.6 is reached, I maintain that taking a breath or two from EAN40 at 130' (or more likely on the way up during a rapid ascent) is not going to be a concern and a diver in an OOA situation breathing EAN40 from a Spare Air has bigger things to worry about.

 

[Lorenzoid]

Sure, nobody "advises even considering breathing such a mix," but the anecdotal reports I recall suggest to me that a diver may very well NOT tox from a few tens of seconds or maybe even a minute of breathing a high ppO2. The difference is we're talking about an emergency ascent, breathing from a tiny canister of gas, which lasts a mere five or six breaths as the diver (regrettably) rockets to the surface, not NOAA's recommended "limits."