Diving Air vs Nitrox

[raftingtigger]

Who gets the benefit? It all depends upon your dive profiles.

If relatively deep, long and aggressive, then you can benefit.

If shallow and conservative, then the dive op benefits ($$$).

So far everyone is mentioning the physiological benefits of Nitrox. You have to also remember there are physiological downsides also. In your Nitrox class you should have been taught several key concepts:
-- less partial pressure of Nitrogen increases your NDLs (benefit)
-- higher partial pressure of Oxygen causes 2 problems: If high enough you can have a seizure (CNS toxicity), and if long enough can cause respiratory irritation (Pulmonary toxicity). Yes this is overly simplistic...
-- ANY nitrogen/oxygen mixture is essentially equally narcotic.

What does that mean IMHO?

If you are diving shallow, but long and repetitive dives than the pulmonary toxicity of Nitrox may be a disadvantage and unless you are reasonably close to NDLs you are getting no benefit. Risk > benefit.

If you are diving deep, and/or repetitively such that you are getting reasonably close to the air NDLs then Nitrox probably is beneficial.

If you are diving profiles (depth, bottom time, repetitive dives) that you have to limit because of air NDLs then Nitrox gives you the option of longer dives. Benefit > risk

Remember that in the case of oxygen; more does not equal better. Nitrox is a trade off between the dangers of oxygen and nitrogen. That is why trimix came around. Less narcosis, less oxygen damage; but much higher costs and I'm sure there are risks I haven't learned.

In my personal diving profiles Nitrox is a waste of money. It seems my buddies air consumption is always my limiting factor. As my buddies get either bigger tanks or get better at air consumption then I might consider using Nitrox.

 

[uncfnp]

So far everyone is mentioning the physiological benefits of Nitrox. You have to also remember there are physiological downsides also. In your Nitrox class you should have been taught several key concepts:
-- less partial pressure of Nitrogen increases your NDLs (benefit)
-- higher partial pressure of Oxygen causes 2 problems: If high enough you can have a seizure (CNS toxicity), and if long enough can cause respiratory irritation (Pulmonary toxicity). Yes this is overly simplistic...
-- ANY nitrogen/oxygen mixture is essentially equally narcotic.

What does that mean IMHO?

If you are diving shallow, but long and repetitive dives than the pulmonary toxicity of Nitrox may be a disadvantage and unless you are reasonably close to NDLs you are getting no benefit. Risk > benefit.

If you are diving deep, and/or repetitively such that you are getting reasonably close to the air NDLs then Nitrox probably is beneficial.

If you are diving profiles (depth, bottom time, repetitive dives) that you have to limit because of air NDLs then Nitrox gives you the option of longer dives. Benefit > risk

Remember that in the case of oxygen; more does not equal better. Nitrox is a trade off between the dangers of oxygen and nitrogen. That is why trimix came around. Less narcosis, less oxygen damage; but much higher costs and I'm sure there are risks I haven't learned.

In my personal diving profiles Nitrox is a waste of money. It seems my buddies air consumption is always my limiting factor. As my buddies get either bigger tanks or get better at air consumption then I might consider using Nitrox.

Actually, there are two ways to benefit. One is longer bottom time, this is the benefit that you are discussing. But most of the rest of us have focused on the reduced nitrogen loading that is only a benefit if they do not dive nitrox to NDL. You can have longer dives or less nitrogen loading but not both. Well, you could split the difference between the two...

How many recreational divers have you see reach pulmonary toxicity levels? How long would a diver have to stay at say 80 feet on 32% to reach toxic levels?

 

[TSandM]

Pulmonary toxicity is simply not a concern for recreational divers using mixes up to 40%. Even technical divers have to be doing a lot of time on deco mixes to push the pulmonary toxicity limits.

CNS toxicity CAN be a problem for recreational divers, but only if they don't respect the MOD of the gas.

If the OPs are gas-limited on their dives, they're not going to be pushing NDLs on Nitrox, so they'll get the maximum benefit from the gas.

 

[raftingtigger]

Actually, there are two ways to benefit. One is longer bottom time, this is the benefit that you are discussing. But most of the rest of us have focused on the reduced nitrogen loading that is only a benefit if they do not dive nitrox to NDL.

Absolutely agree. What I said was if you aren't even reasonably close to the NDL. Sort of like using Nitrox and diving air NDLs was my thinking. As for the pulmonary toxicity, not likely unless the dives are very long and repetitive, not something that will happen on 80' dives. There has been examples on other threads (which one(s) I don't recall right now). My point is that oxygen is also toxic at higher levels. Risk vs benefits need to be considered. Not just a knee jerk "Nitrox is better". In a lot of cases it is, in a reasonable number of cases it is a waste of money, and in a few cases it can cause problems.

How many recreational divers have you see reach pulmonary toxicity levels? How long would a diver have to stay at say 80 feet on 32% to reach toxic levels?

Probably no recreational divers, maybe a research diver or two. See above.

Addendum: If the OP had posted in Basic Scuba discussions my comments would have been inappropriate. Since it was in Advanced Scuba discussions I wanted to bring up (the albeit small) risk side to Nitrox. When ever you use something you should know and understand the benefits AND the risks. The ratio will change depending on the circumstances, the person, and the use. It is akin to understanding the risks and benefits of antibiotic use. Antibiotics can be lifesaving, they can add a layer of safety in some situations, and in others can be harmful without giving any benefit (such as with a viral upper respiratory infection, e.g. a "cold") I can't tell you how many times a day I'm pressured to prescribe an antibiotic for that situation.

Similarly, it is a pet peeve of mine than many new Nitrox divers BELIEVE they will get longer dives on Nitrox when their SAC rate and profile won't let them get anywhere close to air NDLs.

 

[Hatul]

The price of a Nitrox course is not that much compared to the dive-travel bill, so I say yes, get Nitrox certified. Then you have the option of trying a few Nitrox tanks and see if it makes a difference for you. It's nice to have the option. It's also good to expand your knowledge and take a course here and there.

 

[MaxBottomtime]

As an aside, I seem to recall that "Undercurrents" had the results of an admittedly self-directed study that seemd to indicate that couples who dived nitrox on week long dive trips had more sex than couples who dived air.

I believe they were referring to a different nitrox.

 

[AfterDark]

Nitrox certified. A waste of money. I've got 3 tanks O2 cleaned, a waste of money. I'm an air hog and don't get near my NDL limit. I don't feel any different diving EAN or air. I wish I had the money I spent on the course and the O2 cleaning. I may never dive NITROX again.

 

[DevonDiver]

If you were me/he - is there an advantage to us in getting nitrox certified?

On any given dive (same bottom time and depth) you will absorb less nitrogen using nitrox. This, naturally, decreases the risk of decompression sickness (DCS).

Whilst recreational safe diving profiles tend to inherently guard against any unsatisfactory risk of DCS, many hundreds of divers each year do succumb to DCS and require medical treatment. Many of those divers did nothing inherently "wrong" with their dive profile (no fast ascents or exceeding no-deco limits etc)... and no significant (obvious) inclusion of contributing DCS risk factors. Their incidence of DCS is commonly referred to as 'non-blameworthy'. However, it needs to be understood that diving tables/computers only work to a set of pre-calculated mathematical variables - they do not account for individual physiological differences, nor do they account for the presence of 'contributing' factors towards DCS (obesity, injury, sickness, dehydration, cold, exertion etc).

Many divers utilize nitrox for the sake of conservatism alone. They may even plan and conduct dives as though on air (shorter limits), but use nitrox to ensure that physically, their nitrogen uptake is considerably below what they theoretically plan for and track (via computer/tables).

For that reason alone, nitrox may be a prudent option.

 

[supergaijin]

Nitrox is only a good thing for (within MOD) recreational dives- there can be really no argument against it IMO- assuming price is not a problem.

 

[Simon-]

Nitrox certified. A waste of money. I've got 3 tanks O2 cleaned, a waste of money. I'm an air hog and don't get near my NDL limit. I don't feel any different diving EAN or air. I wish I had the money I spent on the course and the O2 cleaning. I may never dive NITROX again.

Can I ask why you got the cylinders O2 cleaned?

Standard dive equipment is fine for up to 40% without O2 cleaning, unless you are using a filling station that only offers partial pressure blending.