Why dive Deep Air?

[k374]

so I notice that when I have my computer in Nitrox mode I have a %CNS counter, usually it's very low as far as I've seen but the only Nitrox dives I have done were pretty shallow, 60ft or so, is there a % exposure limit that one needs to be aware of?

 

[Rhone Man]

so I notice that when I have my computer in Nitrox mode I have a %CNS counter, usually it's very low as far as I've seen but the only Nitrox dives I have done were pretty shallow, 60ft or so, is there a % exposure limit that one needs to be aware of?

Yes; there is a cumulative limit to the oxygen exposure you can safely take in a day. This should probably have been covered in your nitrox course.

 

[Blackwood]

so I notice that when I have my computer in Nitrox mode I have a %CNS counter, usually it's very low as far as I've seen but the only Nitrox dives I have done were pretty shallow, 60ft or so, is there a % exposure limit that one needs to be aware of?

Yah, and I think that since it's expressed as a percentage it should be somewhat obvious what that limit is

 

[k374]

Yes; there is a cumulative limit to the oxygen exposure you can safely take in a day. This should probably have been covered in your nitrox course.

It was covered generally but I don't recall any particular % limit mentioned as a safe limit. For instance..."keep the CNS% under 30%"

 

[Rhone Man]

It was covered generally but I don't recall any particular % limit mentioned as a safe limit. For instance..."keep the CNS% under 30%"

I think the 100% limit is based upon NOAA guidelines.

But (although my memory is a bit hazy) I think on the PADI course they train you to always stay below 75% (and I think that in practice, most dive computers freak if you go over 75%, although I have never done it myself).

 

[Blackwood]

It was covered generally but I don't recall any particular % limit mentioned as a safe limit. For instance..."keep the CNS% under 30%"

The physiological limit is a function of oxygen pressure and time.

"%" is merely a way of expressing how close you are to that limit which makes it easy to add exposures at varying pressures.

At PO₂ = 1.4ATM, for example, the limit is 150 minutes. So if you are at 1.4 for 75 minutes, you're at 50% of the allowable. At PO₂ = 1.2ATM, the limit is 210 minutes. So if you are at 1.2 for 21 minutes, you're at 10% of the allowable. If you are at 1.4 for 75 minutes followed by 1.2 for 21 minutes, you're at 60% of the allowable.

Although there are no bold black lines between toxing and not toxing, by definition the limit is 100%.

 

[David_57]

Why dive deep air? Because you get a good buzz

 

[ianr33]

so I notice that when I have my computer in Nitrox mode I have a %CNS counter, usually it's very low as far as I've seen but the only Nitrox dives I have done were pretty shallow, 60ft or so, is there a % exposure limit that one needs to be aware of?

V-Planner has the default %CNS warning set at 80%

By taking air breaks many, many divers have done dives where the CNS is hugely over 100%

Most recreational divers (32%, pO2 <1.4) will never get anywhere near the "limit."

 

[drbill]

I can't remember if I've already posted in this thread and won't take the time to read all of it.

When I was gathering footage for a future episode on "deep ecology," I routinely dive to a basement depth of 200 ft on air. However, I did so after about two months of conditioning myself at deeper and deeper depths to assess my response to narcosis. I was quite functional at my maximum depth... able to locate, frame and smoothly follow subjects while I videotaped.

However, I would not classify any of those dives as "bounce" dives. They were often in the 50-60 min duration range, involving a number of deep stops and long stays in the shallows (10-20 ft). Our submarine profiles off Catalina's leeward side allow us to do such dives with ease by simply following the slope back up.

I do NOT recommend deep air dives (or solo diving) to any other diver since I do not know their capabilities, training or response to emergency situations.

 

[hg frogman]

In France, adequately certified recreational divers (French CMAS *** divers and above) are allowed (by French law) to dive down to 60 meters/200 feet using only air (also for deco). Same for commercial and military divers. Whether good or bad, it keeps it simple (say stupid if you prefer).

So what people call "deep" or "reasonable" is also a matter of culture.

By the way, why penetrate in wrecks ? I wouldn't do that for leisure .