Nitrox

[triton94949]

...A better way, IMO, is to dive conservatively using a nitrox computer set to the right mix. ...

I agree with that opinion as well. A good nitrox computer will beep at you if you go too deep for the nitrox mix. If you set the computer on air while you dive nitrox, you could end up making a really big mistake.

 

[Shoc369]

I feel MUCH better after diving on Nitrox. My fatigue level is greatly reduced vs. diving on air. So I would definitely recommend getting your EAN cert.

That being said, I personally would never dive Nitrox on an air computer. I agree, you really could make a big mistake.

If you are diving WELL within the limits of the EAD (Equivalent Air Depth) you may feel comfortable doing it, even though I wouldn't do it and don't recommend it. But if you aren't diving WELL within the limits of the EAD, your dives would be really stressful just watching and worrying about your depth.

 

[Tim Ingersoll]

An air computer will always err to the side of caution, though, right? I have a trip to Cozumel slated for May, and although I am considering a nitrox cert before then, I really don't want to have to shell out for a new computer, too. My primary motivation (for now, anyway) is extending my margin against DCS on dives shallow enough for nitrox, not extending bottom time.

Rent a nitrox computer from the dive op and dive with two computers. You will learn alot about the differences and still not have to buy a new computer. I bought a nitrox capable 2nd computer and use it with my air only computer. I never max out my air computer or even push it to the stops and never go below 100 feet. I have found that the biggest differences in bottom times are at the shallower depths. Good luck!

 

[J1M1]

P02 levels are next to impossible to max out.

not following you?

 

[ggunn]

I agree with that opinion as well. A good nitrox computer will beep at you if you go too deep for the nitrox mix. If you set the computer on air while you dive nitrox, you could end up making a really big mistake.

Oh, I agree, but a new computer may not be fiscally possible by my May trip. What I would do would be to only use nitrox on the second dive where we'll be staying well above O2 toxicity depths. And, of course, I won't be following ANY course of action solely based on what you guys say, no offense intended. If and when I take a nitrox course, I will base what I do afterwards on what I learn there and by talking it over with my instructor.

 

[Charlie99]

An air computer will always err to the side of caution, though, right?

What I'm advising against is what I ended up doing in Florida when diving some wrecks. I inadvertantly left my computer on air, even though I was diving EAN36. I recalculated in my head, and ignored the deco obligation. I did end up doing the 7 minute required hang so I wouldn't lock out my computer, but knew I was in reality well away from the deco limit.

Trust me. It will be very tempting to continue on for a while when doing the 2nd dive of the day on the C-53 wreck and your computer goes into deco while you still have move than 1500psi in your tanks.

 

[Wristshot]

For what it is worth, I would suggest that you consider taking Nitrox training. Then you would understand all of this better. (past experience has indicated that you are intelligent enough to grasp it all) Then you would be in a better position to determine whether it is a good idea to use an air computer for Nitrox. (by the way, air is 21% Nitrox!)

I do find that diving with Nitrox was nicer in most cases. YMMV. Some say they are much less tired after a EANX dive, others claim it is BS. Take the training, try it, then you decide for yourself.

Depending upon who you dive with and how you dive, using EANX in Cozumel may not get you longer bottom times, but it should decrease your Nitrogen loading. If you are surfacing based on the consumption (etc) of other divers on a boat, then you probably won't gain bottom time, but you will be in a lower Nitrogen group (than you would be on air) at the end of your dives.

What you will be trained on is that while too much Nitrogen is very bad, there is a reason that too much O2 is called Oxygen TOXICITY. Repeat: TOXICITY. Yeah, I know, you already knew that, but it never hurts to remind the world.

In Cozumel since generally Nitrox won't increase your bottom time, it is usually used to lessen the Nitrogen loading, and usually on the second dive. Many guides use EANX on the second dives, so that they can do 4 dives a day without (as much) worry about Nitrogen. In general it is easy in Cozumel to only use EANX when you are diving at a location with a hard bottom that is shallower than the depth for OX-TOX.

IMO, the dangers of diving EANX on an air computer are as follows (and as listed or alluded to previously)
1) Danger of exceeding the max depth for PPO2. Don't. I just don't use EANX when I am in water deeper than the max for the mix.
2) Danger of adjusting time based on the fact that you "know" that you were extra conservative based on the computer. That is like the people that set their clock ahead so that they can make it to work on time, then ignore the clock because they know that it is set ahead.

To Sum up: Take the training, learn the material, then dive with what you have, in a safe and educated manner. Down the road you pop for the EANX computer and continue to dive safe.

Wristshot

 

[triton94949]

... If and when I take a nitrox course, I will base what I do afterwards on what I learn there and by talking it over with my instructor.

When you take your nitrox class, they will teach you the additional requirements and procedures that you need to follow for diving with nitrox. In a nutshell, it goes like this:

1) Plan your dive. Maximum depth is your main consideration with nitrox, since the oxygen richness of nitrox causes your max depths (called MODs) to be shallower than with air.

2) Choose your mix. Generally you will have two choices: EAN36 and EAN32. However you could order any mix from 25% to 40% oxygen. Most nitrox divers use 32%. Some use 36%. A few order a specific mix somewhere in the range of 25% to 40%. For EAN36 your MOD will be 95 ft. But you need to learn how to calculate that, in case you choose another mix between 25% and 40%.

3) Determining your maximum NDL times for various depths down to your MOD. Nitrox gives you longer NDL times. There are nitrox tables that will do this for you, or you can learn the equivalent air depth formula and then convert your nitrox depth to an equivalent air depth, and then use an air table.

4) A computer will let you dial all the above information in. Then it will tell you your MOD and your NDL times. That is what is nice about them.

5) You could make a chart, memorize it, and then do the determinations (rough calculations) in your head, without a dive computer. You still need a depth gauge and a timer, or a bottom timer (which combines a digital depth gauge with a digital timer).

If cost is a major factor for you, then you may want to look at bottom timers now, and forget about getting a dive computer. Bottom timers are much more accurate than an analog depth gauge combined with only a watch, and they function like a computer that has been set to "gauge mode."

Enjoy your class! Nitrox is fun. And the principles of oxygen exposure, equivalent air depth, MODs, and increased NDLs are fun as well.

 

[Wristshot]

Gordon,

In some locations, especially dive destinations, your choices may be very limited in regards to what mixes are available. In general 32% and 36% are the most common. For the average diver, only 32% will be available in Cozumel. The MOD is about 107 feet as I recall. Plenty deep for most things in Cozumel.

Wristshot

 

[MMM]

I haven't had any problem getting 36% with Blue Angel or Living Underwater.