How does Nitrox work?

[DevonDiver]

The other way to look at it...as a benefit for less experienced divers... is that for any given dive, it will increase your level of conservatism, because you are reducing your nitrogen uptake. In the event of an uncontrolled ascent etc, then it means you have a decreased likelihood of getting a DCS hit.

When teaching, I have used Nitrox on occasions to increase my conservatism because I have been suffering from pre-disposing factors (illness/dehydration). My only other option would have been to set my dive computer to a more conservative setting....thus penalizing my customers on that day with shorter dives. I don't like to do that...and sometimes, as a professional diver, you still have to work, even if you're ill or recovering from illness.

 

[DandyDon]

Don,

If DAN says it has no benefit for most recreational divers... who am I to disagree.

My personal experience as it relates to Nitrox. I'm certified and an Instructor in it's use. I've been Nitrox Certified since 2000. I dove it in 2000 and 2001 because back then I didn't know any better. I had been convinced by my LDS I had to have it.

Then I did some research and read articles in DAN's magazine over the years and learned that it was for the most part (and lack of a better term) a bunch of fooey.

I stopped using Nitrox because it cost an extra $100 or more a week on a trip and for tanks locally it was $3 - $5 more per fill if I was diving locally. Based on what I had researched the minimal benefit or lack thereof entirely was not worth the extra investment.

I just kinda doubt that DAN used those words and would be interested to the see the article. You mentioned in a subsequent post that you "went to the DAN website to see if there was an easy way to pull up older articles and I couldn't find a way... but they exist. If anyone knows how to find artcicles from old DAN magazines online - can you please help..."

1: Log in at DAN sites;
2: Go to Dive Medicine and Medical articles as illustrated on the pic;
3: Use Search circled in upper right.​

click pic for larger view
​

The whole thing about Nitrox making you feel better after a dive has also been refuted by DAN. At best it has a placebo effect... and I'll agree that may be enough for some people. We all know perception can be far more powerful than reality.

So if you truly believe you feel better because you dive Nitrox - you probably do... but it has nothing to do with the Nitrox...

Cheers to "feel good" diving!

I know that part is unsupported and I don't buy it either. But I do view Nitrox as a tool, not the most commonly used one in my tool box, but one I always want in there in case I want to use it.

I've had experiences where I had to end my wreck dive early because my boat-pic air diving buddy was close to his NDL and wanted to ascend, and I always descend and ascend with my bud, whenever either of us calls the dive, no arguing. One that comes to mind was a newbie, but better on consumption that me - just out of time.

I've had experiences where the captain made all divers take a longer SI to keep the air divers safer.

I've just been posting on a thread with a diver whose GF took a hit after diving 5 air dives. Dehydration was the obvious contributing factor in that case, but vacation divers do that. Why not give them the $100 tool?

I've seen others leave in ambulances over the years.​

Here in NC it is very common for off shore dives. Our dives tend to be on the deeper side and it is common for a lot of divers to be diving larger tanks- 100s and 120s are common. The combination of multiple deep dives and larger tanks easily puts us into deco without nitrox.
OP- Here is some online info on nitrox you may find interesting. Nitrox Course Outline

Yep, for NC wreck diving I've done back to back wreck dives on Nitrox with large tanks and still went to my NDL even with my lousy consumption rate, also in the St.Lawrence and Florida. One on NC wreck I saw a diver who shouldn't have been on the boat, but it happens that they are at times, diving air with a Nitrox diver - and when he approach NDL, they split! I don't do that, but they did - leaving her on the bottom without a buddy, him ascending alone and sure enough - his reg failed on ascent. Fortunately he caught up to another diver to donate.

Second... I'm in full agreement that successive deep dives without an adequate surface interval will require Nitrox - to avoid going into decompression mode on your computer or being told no to the dive - if you're using tables. I'm also in agreement that bottom time is limited even on your first deep dive without Nitrox.

The point being made however is that most recreational divers aren't trained for those types of dives to begin with (OW to 60ft) and most never go that deep (100ft +) at anytime in their diving careers.

I think you're just flat wrong. I see OW newbies going to 100+ft frequently on my trips. I don't mind doing 100+ft on air at all on a 2 dive day, but on a 3-dive day - I'm willing to pay even Cozumel rates for one tank of voodoo gas.

The Nitrox card was much more expensive when you and I got ours, but it's only $100 including everything now, no dives required - yet still prepares the diver to be a safer diver when it's indicated. Such a good idea and I just don't get your opposition.

 

[elan]

My wife and I do liveaboard trips with many friends. They all dive Nitrox except for us. We've been doing it for years now (8 - since 2001.) We all get in the water at the same time, we all do the same dives and we all get out of the water at the same time. Virtually identical profiles. Same surface interval times etc... We'll sometimes do 5 or even 6 dives a day... In the last 8 years there has not been one dive where I couldn't do the exact same profile as any one of them.

Now I'll grant you that my nitrogen loading is higher than theirs... however my loading is still within my computers limits.. and the computers algorythym limits are so conservative they make the Navy Tables look like jumping off a cliff.

This argument has nothing to do with Nitrox then, It's just computer vs. tables comparision.

 

[DevonDiver]

Now I'll grant you that my nitrogen loading is higher than theirs... however my loading is still within my computers limits.. and the computers algorythym limits are so conservative they make the Navy Tables look like jumping off a cliff.

Within computer limits? And yet, divers still regularly get bent within computer limits.

If you can do the same dive, same profile, same bottom time, same enjoyment...and stay further from your limits whilst doing so.... what sort of logic is there to refute that???

People spend hours on this forum debating which algorythm keeps you safer.... how to DIR....how to practise this and that emergency drill...

...and yet here is an easy option for any diver...that keeps them a little safe, and more conservative, in the water.

why not?

I know that putting my post on as I did will draw some attitude from those who push Nitrox on every customer. That is to be expected. They're all out to make a buck and posts like this one don't help that ideology. My posts are there to educate the consumer on the truth. This truth is something they can just as easily obtain through diligent research.

Personally, I don't 'push' courses on anyone. I am not out to 'make a buck'... I only ever desire to have a happy, satisfied customer base that comes back to me again and again for good value, beneficial training.

i'll sell nitrox to anyone...why? Because they will see the benefits of it on their first 2 dives (square profile, wreck dives...which is what my location is famous for).

I won't give you attitude either.... but I do wonder at your viewpoint...and why you would discourage divers from seeking extra conservatism and safety from such a simple, swift and inexpensive course of education?

as others have said...nitrox is just another tool in the toolbox. The same (but cheaper and easier) than doing a deco diving course...or investing in larger cylinders or a twinset. It just happens that this tool will increase conservatism and offer a greater spectrum of diving opportunites...along with more minutes under per dive.

Divers may not dive deep....probably because they don't see the point due to limited bottom-times. Now they have the option to enjoy deeper, longer dives. Happy days!

 

[Blackwood]

Everything said so far is wrong. The correct answer is: magic.

 

[Cave Diver]

Everything said so far is wrong. The correct answer is: magic.

I'm sorry, this is incorrect as well.

Everyone know that nitrox is not magic.

It's actually voodoo!

 

[Teamcasa]

Within computer limits? And yet, divers still regularly get bent within computer limits.
<snip>
...and yet here is an easy option for any diver...that keeps them a little safe, and more conservative, in the water.
<snip>
i'll sell nitrox to anyone...why? Because they will see the benefits of it on their first 2 dives (square profile, wreck dives...which is what my location is famous for).
<snip>
as others have said...nitrox is just another tool in the toolbox.... It just happens that this tool will increase conservatism and offer a greater spectrum of diving opportunites...along with more minutes under per dive.
<snip> Now they have the option to enjoy deeper, longer dives. Happy days!

I feel exactly the same way. Nitrox is a simple, safe and inexpensive to enjoy longer dives and still be safe. Like many things, there are no guaranties you won't get bent but why not reduce you chances? How it works is not rocket science but I am leaning towards voodoo.

 

[offthewall1]

The following are article excerpts relating to the thread. Where notable... the sources are indicated. I have not had time to find the DAN ones... they are not on the website... at least not that I could find... but here are some others that support some of my points of contention.

Article Quotes:

"Is nitrox safer than regular air?

This is one of the most popular myths regarding nitrox diving. People usually refer to the avoidance of DCS (decompression sickness) when they claim EANx to be safer than air.

Let's take a look at the diving accident statistics! DAN (Divers Alert Network) has statistics of DCS cases in the USA, which is based on DEMA/NUADC and PADI New Diver Benchmark reports. According to them, the probability to get DCS by air diving is about 0.004% (1 to 25000). Based on this number, and on the PADI Undersea Journal 3/97 magazine, the probability to get DCS by air diving even once during 500 dives is 1.98% (1 to 50). The risk is 1.49% in nitrox diving in same amount of dives. So... so far the difference is marginal.

But an accident doesn't have to be DCS only, and when diving with nitrox there are several other concerns too that air diving doesn't have. Gas blending, analyzing errors, oxygen clean equipment, CNS clock etc. may also be a source of an accident. In this point I have to say that nitrox diving is not dangerous when done right, but these points have to be counted when people talk about safety. So nitrox diving is safe, but not safer than air, generally speaking.

Myths

Besides the safety myth above, there are several myths regarding nitrox diving:

People who don't know much about nitrox think sometimes that it is used for deeper dives. Well, it is not, but it is mostly used on mid deep dives, ranging from 20-40 meters (~60-130 feet). The more oxygen you have in the mix, the shallower the MOD (maximum operating depth) will be.

It is also a common misunderstanding to think that it causes less narcosis. This would be due the fact that it has less narcotic nitrogen. But oxygen is also narcotic, and according to some references it is maybe as narcotic as nitrogen, and together with nitrogen it could be even more narcotic (Bennett 1993, Inert Gas Narcosis, the Physiology and Medicine of Diving, 4th edition)!

There are also no advantages in rare embolia cases (The Undersea Journal 3/97).

Why should one dive with nitrox?

Simply: to gain more bottom time and to have shorter surface time intervals. For example, if you dive two dives to 20 meters (66 feet) with one hour surface time, the no decompression limited bottom times will be 45 minutes and 24 min, respectively. Now, if you do the same with EAN40, the bottom times rise to 98 min and 61 min, respectively. (PADI diving tables)

Another example: Two 25 min dives to 25 meters (83 feet). The surface time will be at least 2 h 19 min (in no decompression limits), but with EAN40 you don't even have to have the surface time! (PADI diving tables)

EANx is also used in technical and commercial diving to shorten the decompression times.

How much does it cost, where do I get it and who can dive with nitrox?

Nitrox cost much more than air, maybe 1.5 times as much roughly (Sometimes more, sometimes less. Ask for your local diving center. Several diving centers fill nitrox, but you have to be certified first."

Points: 1. Nitrox cost more than air. 2. Nitrox is at best marginally safer than air. 3. The increased risk of other errors associated with diving Nitrox make it's safety questionable. 4. There is no benefit other than increased bottom time / shorter surface interval

We can debate this all day long. There are opinions and evidence on both sidesof the debate... but there are reasons Nitrox was not introduced into recreational diving for so long... 1. It isn't necessary, 2. It wasn't considered safe and 3. The risks of recreational divers using it outweighs the miniscul benefit to them.

Technical and Commercial divers had been using it for years before recreational divers... and they needed to. They still need to today... and I'll continue to believe the risks outweight the benefits in the recreational arena.

 

[DandyDon]

That is a bit different that your previous claims alluded to DAN....

""There is no benefit other than increased bottom time / shorter surface interval"

OK, that's why I dive it when I do, and when I am diving wrecks and/or with a tight butt skipper - I hope that everyone on the boat is. I like a large tanks, longer BTs, and shorter SIs before repeating on those trips.

For $100 US and 3 hours class time, any continuing diver can reasonably do that, so we don't have to say "Damn, sorry you can't go on this one. You 'waited until you needed it,' and now you do - but you can't do it that fast."

 

[offthewall1]

A little off subject... not really a hijack - just some more food for thought on another topic I talk about often on Scubaboard... that is that opinions on here are just that... and virtually every thread on the board that turns into a debate... has about 50% of the people on one side of the argument and 50% on the other side.

Here is my point... Dandy Don and I (I'm using him because he often likes to refute things I post on the board) are often on two opposite sides on a debate. In most cases neither of us are wrong per se... but we disagree.

Don has been on the board since 2003... myself a more recent join in 2007. Since 2003, Don has racked up a very impressive 393 thanks for his postings. I admire that because it means Don takes a lot of time to put up useful and thoughtful posts. On average Don receives 65.5 thanks per year since 2003 or more than 1 per week. Now Don has had to make 28,764 postings to receive those 393 thanks or 73.2 posts per one thanks received.

Since joining in 2007, I have totaled 127 thanks... or an average of 63.5 thanks per year (very similar to Don on an annual basis.) The difference is I've only had to make 639 posts to receive those 127 thanks... or just 5.0 posts per one thanks. If I had Don's number of posts, I'd have more than 5752 thanks to his 393.

Not that this indicates I'm better than Don in any way, but rather that I only post relevant... pointed, direct and knowledgeable answers to important questions being asked by divers. i don't come on with a lot of fluff.

The point is most of what people post on here is just fluff back and forth between people who have nothing better to do than sit at a computer all day. Some of us jump on - answer a question or two - then jump off and let the fisticuffs fly.

In any event, Don and the others are not wrong in saying Nitrox has benefits... they are wrong in saying it has benefits for everyone regardless of the type of diving they are doing. My original post said simply this... you can go back and read it - "Once you've decided the type of diving you'll be doing, then you can worry about Nitrox."

Others have adeptly pointed out it's limited range in providing benefits to recreational divers... and if you're diving often enough within those ranges... maybe you should consider Nitrox.

Don, as for your last post... again... there is NEVER a "need" for Nitrox. A "Want" a "Desire" perhaps... but never a "need" in recreational diving.

Cheers