Another (legit) nitrox ?

[Dive-aholic]

It's not likely you will reach your max daily OTUs doing recreational dives, especially diving with a dive op.

 

[wjefferis]

hey all-
i have a question i haven't seen asked about nitrox .
i have seen some folks recommend diving nitrox using air tables(or comp) for an added degree of safety. i thought this was a good idea, but we are going to Rotan soon. so here is the ?
if doing multiple, repetative dives (say 4-5 dives a day for a week) to 50-90' is there a danger of too much o2 buildup? just a thought... thanks!

As other people have commented on, there is a concern for CNS buildup of o2 in the system from diving NITROX. Most computers I have seen recently deal with this by monitoring your oxygen limit fraction. My computer warns me if it gets too high (never happened) and lets my know what percent of oxygen my central nervous system has been exposed to during and after my dive. If you are going to be doing alot of dives I would recommend that you get NITROX certified before you go on your trip. It will enhance your safety and help your repetitive dive times. Just make sure you have a NITROX computer, diving tables for that many repetitive dives will leave you on the boat figuring tables while everyone else is out enjoying themselves.

 

[jon m]

thanks all for the replies...
of course i will be taking a nitrox course before i go. i would not want to dive with an op that allowed me to dive enriched air without it...

 

[mello-yellow]

When I took Nitrox course, I tried to come up with a repetitive sequence of dives which would exceed your CNS limits while remaining in "recreational limits" -- no-decompression, PPO2<=1.4, EAN40 or less. The answer is -- it is physically impossible. No matter how deep or how shallow you go, you hit NDL limit long before CNS limit. But yes, if you don't know what you are doing you can easily get into toxic levels of PPO2 -- and that is BAD.

 

[SteveAD]

When I took Nitrox course, I tried to come up with a repetitive sequence of dives which would exceed your CNS limits while remaining in "recreational limits" -- no-decompression, PPO2<=1.4, EAN40 or less. The answer is -- it is physically impossible. No matter how deep or how shallow you go, you hit NDL limit long before CNS limit. But yes, if you don't know what you are doing you can easily get into toxic levels of PPO2 -- and that is BAD.

Impossible on a single dive perhaps, but doing enough repetetive dives it is certainly possible.

 

[scubadobadoo]

IMHO, put your computer on nitrox mode when diving nitrox. That's why one buys a nitrox computer. Tricking yourself and your computer can actually hurt you, and it hasn't lead to fewer cases of DCS in the recreational dive world either.

I suggest that one concentrates more on HOW one dives instead of WHAT one dives with when looking to decrease the chances of a DCS hit.

Do take the nitrox course. It will greatly enhance your knowledge of dive table theory. Oh, and have a blast in Roatan!!

 

[mempilot]

My main concern with this thread is that shoud one decide to dive 32% while using a computer set to air or 21%, sure the computer will give you a very conservative bottom time, but....that same computer will give you a MOD that will be WAY to deep for the 32% that is being breathed. Forget that little tidbit of information and you might have a very bad day.

While I agree with you in theory, I feel that a diver should plan there dive with at least a basic understanding of the gas they plan to use. So if they plan on doing a dive to 100 fsw, they should choose the correct mix based on desired PO2 and then just set the computer to AIR for conservatism if that is what is desired. With a hard bottom of 100 fsw, this should not be an issue, especially if the desired PO2 follows the recommendations of the various agencies. Now, on a deep wall where target operating depth and max operating depth can be quite a bit shallower than the hard bottom, then this technique would need considerable more thought and attention.

 

[Dive-aholic]

IMHO, put your computer on nitrox mode when diving nitrox. That's why one buys a nitrox computer. Tricking yourself and your computer can actually hurt you, and it hasn't lead to fewer cases of DCS in the recreational dive world either.

I suggest that one concentrates more on HOW one dives instead of WHAT one dives with when looking to decrease the chances of a DCS hit.

Do take the nitrox course. It will greatly enhance your knowledge of dive table theory. Oh, and have a blast in Roatan!!

What happens when your computer fails or the battery dies and you have to start diving tables or off a rented computer? Now the OTUs are no longer being calculated by the computer. It's never a good thing to rely on a computer without being able to work the numbers...

 

[Steve SDI/TDI HQ]

I just took the Nitrox course last night. It was TDI's version.

Great class, one of the better coursebooks I have seen, and I would say that I am highly confident of my EAN knowledge.

I suggest taking the usually one day course, rather thanseekng advice from the internet or other dive buddies. It's well worth it.

Thank you for the feedback!

And good advice to the OP. Since Jon M is taking a course, multi-dive multi-day limits should be covered.

In general tracking OTUs (pulmonary toxicity) for dives within sport limits is a waste of time, since it is impossible to reach a level where lung function is compromised.

HOWEVER, CNS tracking (single exposure and 24 hour exposure) MUST be noted and NOAA guidelines followed. And regardless of what some have posted here, is possible to exceed the 24-hour allowable limits set by NOAA. Your course will cover this.

 

[raymond phule]

And regardless of what some have posted here, is possible to exceed the 24-hour allowable limits set by NOAA.

Might be possibly in theory if you dive a lot. Seems pretty difficult in practice though. Do you have a series of no-deco dives that exceed the limit? I believe it's not possibly with ean32, might be possibly with ean36 if you have something like 6 dives at the no-deco limit over a 18 hours period.