Nitrox: No Decompression Limit - Ascent

[Steve_C]

There really is no difference diving on air or nitrox in terms of procedure. NDL is how much time until you will be in deco. If you go up you will get more NDL. If you go down you will have less NDL. You have NDL with air also. In fact on a given dive you will run out of NDL quicker with air than with Nitrox. The idea is you just dive, make sure your NDL does not go to zero and ascend carefully before you get low on air.

Now that is the theory. Reality is that sometimes stuff happens. Regardless of whether you are diving Nitrox or Air, you should have read the manual and know what your computer will tell you if you do go into deco. A slow ascent and you may go out of deco. On the other hand it might give you a ceiling and an amount of time to spend below that ceiling.

An aggressive dive master/guide put me into deco on the very first dive with a new computer. But I had read the manual so no problem.

 

[Lateralus]

As you ascend your NDL time will increase. I suspect when you got to the top of the wall or closer to your safety stop depth your NDL went to 99 minutes. That means you could stay at that depth 99 minutes before entering deco. Is the computer new to you?

boat

Correct. The computer is new to me. I will read up on it tonight.

 

[tomfcrist]

I’m gonna gonout on a limb here and say you put your computer in deco...thus the Deco warnings of your computer.

You would be well served to plan the bottom time before you splash...you can do that before wvery dive.

Put in your nitrox mix...let the computer go into the ever cycling planning mode that (most?) all do on the surface...wait for your planned depth to show up and plan for that as your max bottom time. Try to stay out of deco...in fact, it’s not that big a deal to stay a few minutes on the right side of your NDL...especially if you aren’t comfortable doing deco(or aren’t trained for it), or are unsure of the true functionality of your computer.

My 2psi.

 

[IncreaseMyT]

Sounds like your PO2 was set lower than 1.4 and your computer thought you were too deep for your mix.

Doesn't sound like you were deep enough long enough to run out of NDL to me.

 

[Lateralus]

AquaLung i300

What model is your dive computer? If you bought it at your LDS, go there and tell them you are confused with it and have them explain it to you hands on. On my computer, if I have an ascent rate violation, it will give me a ceiling and indicate I have to stop for a bit. Somewhat confusing the first time it happened.

 

[Nick Steele]

Sounds like a lot of good advice here.

I think some confusion comes from you not knowing what the computer was telling you at the time and is making us guess. I also don’t think you hit your NDL and either a) ascent rate was above 30ft per min or b) just being a new computer you didn’t understand it.


Do you remember exactly what it was showing at the time?

 

[The Chairman]

My computer was just telling me all sorts of reading.

Could you describe this more precisely?

www.divenav.com can probably help you there.

 

[Lateralus]

Sounds like a lot of good advice here.

I think some confusion comes from you not knowing what the computer was telling you at the time and is making us guess. I also don’t think you hit your NDL and either a) ascent rate was above 30ft per min or b) just being a new computer you didn’t understand it.


Do you remember exactly what it was showing at the time?

Don’t recall.

I think the consensus is correct. I’m just not familiar with my dive computer. Going to read up on the manual.

Thanks for the help.

 

[Lateralus]

Thanks for the help everyone. Seems that the issue was just me not be understanding my dive computer properly.

What I thought was a warning was just he computer telling me that I was super okay.

 

[BoltSnap]

Why not go back to your LDS where you bought your computer and have them explain how to use it to you and also for them to check your log in addition to the settings you already have on the computer and try to determine what you did wrong/right?

You should also go to this website and sign up for their online nitrox and dive computer courses. They inexpensive and do an excellent job in explaining what's what with nitrox and dive computer use:

Dive Computer Training