Catalina U/W park dive report.

[scjoe]

Coolhardware52,

When you make the point that 30% is a much greater concentration than 23.5%, you miss the point that the quote was referring to "non-flamable materials" and that there was a prior quote stating:

"Oxygen enrichment of the atmosphere, even by a few percent, considerably increases the risk of fire."

I am not arguing for or against 23.5% or 40%, I am simply trying to point out that there are manufacturers, trade groups, regulatory agencies and others that have adopted the 23.5% standard. OSHA has adopted 40% only for commercial diving. According to Luxfer, one entity, the US Navy re-thought its 40% standard and lowered it to 25%. Whatever limited discussion you had in your Nitrox class about these standards, it clearly did not cover how the standard was arrived at by all of these different groups or you would be able to explain it. The fact that no one on this board has been able to do so suggested that there really is no meaningful discussion about the different standards in the nitrox classes.

You are asking for data that shows 23.5% merits O2 service. The conclusions of multiple entities who have set their standards at or near that level is data. What test data has the dive industry supplied in support of its 40% rule?

In this thread, people have used the speed limit analogy, but I think a better analogy is cigarette smoking. Many of us know people who have smoked their whole lives and never gotten cancer and people who have never smoked and died of cancer. In fact, there are thousand of people in both groups. That fact has been used by the tobacco industry for years to support its argument that there is no proof that cigarrette smoking causes cancer. The Surgeon General has reached a different conclusion. Both sides have used qualified doctors and scientists, real world data, and real world analysis. They have come to different conclusions.

If you work for the tobacco industry or live in the tobacco states, you are more likely to accept the industry's interpretation of data. If you work in a different industry or live in different states, you are more likely to accept the Surgeon General's report. In neither case do many people actually understand how the positions were arrived at.

I put it to you and the rest of the board that as divers we accept the 40% rule because that is what we were taught by the industry we are in. We have no idea how it was arrived at. Did the industry, as Luxfer suggests, just grab onto an OSHA rule designed only for commercial divers. We presume, or at least hope, that the rule was not arrived at based solely on anecdotal evidence, but that is all we use to defend it when presented with a different standard used by several different groups without knowing how they selected their standard. If the lack of accidents is sufficient, then we should not retro fit buildings for earthquake safety. Afterall, there are a lot of very old buildings that have survived a lot of earthquakes that are not up to code. If they did not fall down in the last earthquake, they must be safe enough.

In the case of cigarettes, most of us are not able to determine on our own whether the Surgeon General or the tobacco industry is right, but we instinctively distrust the industry and opt for the more conservative interpretation of the data. In diving, we seem to turn this process around by distrusting the regulatory agencies and putting our faith in the industry.

LAJIM has calculated that under pressure in the tank the mix does not matter, but he acknowledges that the concentration outside the tank does make a difference. Since the gas mix does come in and out of the tank during use and when being filled
there seems to still be a mix issue. Presumably contaminents in the tank can make their way to the exchange point where a fire may occur. That then gets us back to the question of at what % above 20.9% does the risk of a fire increase to the point that we should take steps to reduce the flamable materials. Most safety experts in diving say 40%, safety experts in the general compressed gas industry, certain tank manufacturers and the US Navy say between 23.5% to 25%. Your mileage may vary.

 

[LAJim]

I agree that the prudent thing to do is, on an industry-wide basis, greatly reduce the introduction of lubricant into compressed gases (including air) used by divers. Nitrox is no longer an exotic gas mixture. Given the wide incidence of real DCS and wider precautionary treatment for suspected DCS, moving toward even wider adoption of nitrox as a dive gas of choice is inevitable. These things reach a tipping point. Once most dive boats and dive shops offer nitrox fills an operation that does not provide that option is starting to look vulnerable when a recreational diver patron suffers DCS.

When I took the basic PADI course I got the sense that dive computers were exotic items carried by technical divers or gadget freaks (i.e., guys like me). Instead I can not remember anytime I've been on a dive boat in SoCal where a cetified diver was using tables (except, in theory, my wife - before I upgraded and gave her my old one). Nitrox is going to be the same way when it reaches the tipping point. People will dive Nitrox even with 3 dive 40 ft. 60 min. profiles because it gives them a safety margin or because they feel better using it. Sure you have to pay for it but you've already put down $120 to get on the boat and the price of nitrox will drop.

My point? When 2/3 of all active divers in the US are using nitrox some of the time and 1/2 are using nitrox all of the time the default for all tanks will be nitrox service, and air compressors that possibly introduce lubricants to the tanks will have to be replaced.

Jim

 

[cool_hardware52]

Coolhardware52,

When you make the point that 30% is a much greater concentration than 23.5%, you miss the point that the quote was referring to "non-flamable materials" and that there was a prior quote stating:

"Oxygen enrichment of the atmosphere, even by a few percent, considerably increases the risk of fire."

Maybe your nitrox class was a bit abbreviated. It is pretty well known that raising the either the pressure, or the fraction, or both of O2 affects the "flamablity" of most materials. That's why you need specific materials for O2 service.

I am not arguing for or against 23.5% or 40%, I am simply trying to point out that there are manufacturers, trade groups, regulatory agencies and others that have adopted the 23.5% standard. OSHA has adopted 40% only for commercial diving. According to Luxfer, one entity, the US Navy re-thought its 40% standard and lowered it to 25%.

It would be nice if regultory bodies selected standards after a rational examination of geniune, pertainent, evidence. This is unfortunately often not the case. All kinds of agendas creep into the formulation of laws, and very often the practical issues of enforcement trump reason.

Whatever limited discussion you had in your Nitrox class about these standards, it clearly did not cover how the standard was arrived at by all of these different groups or you would be able to explain it. The fact that no one on this board has been able to do so suggested that there really is no meaningful discussion about the different standards in the nitrox classes.

I find it enormously presumptious for you to comment on the extent of my training, or the range of subjects discussed by my instructors. OSHA CFR Title 29, XVII, Subpart T, 1910.430 was discussed, and the fact that is a commercial diving regulation for heliox was pointed out. The USN regs, limits (25%) and cleanliness standards were also discussed. My instructors goal was to specifically illuminate the lack of uniformity in regulation, and the uncertainty and potential liability this creates for the recreational diving community.

There was no discussion of how each of these regulatory bodies determined their limits and guidelines.

You are asking for data that shows 23.5% merits O2 service. The conclusions of multiple entities who have set their standards at or near that level is data. What test data has the dive industry supplied in support of its 40% rule?

If there were stacks of "crispy critters" and smoldering building foundations as the result of 23.5% O2 fires they would be widely cited. Again if you are in possession of such data please show me.

If there were long lists of scuba related accidents even remotely related to the use of 40% and under, nobody would be pumping nitrox commercially using any method, and you would not be able to purchase "nitrox" ready regs, tanks, etc. Why? because the insurance industry would not provide coverage. Betcha the lawyers for the big reg manufacturers checked this out pretty well.

In this thread, people have used the speed limit analogy, but I think a better analogy is cigarette smoking. Many of us know people who have smoked their whole lives and never gotten cancer and people who have never smoked and died of cancer. In fact, there are thousand of people in both groups. That fact has been used by the tobacco industry for years to support its argument that there is no proof that cigarrette smoking causes cancer. The Surgeon General has reached a different conclusion. Both sides have used qualified doctors and scientists, real world data, and real world analysis. They have come to different conclusions.

If you work for the tobacco industry or live in the tobacco states, you are more likely to accept the industry's interpretation of data. If you work in a different industry or live in different states, you are more likely to accept the Surgeon General's report. In neither case do many people actually understand how the positions were arrived at.

Your tobacco example is a Red Herring. It's pretty well accepted that the Tabacco Industry knowingly lied for years. I don't think anybody is lying about the risks of Nitrox, in order to set lower limits.

I put it to you and the rest of the board that as divers we accept the 40% rule because that is what we were taught by the industry we are in. We have no idea how it was arrived at.

No argument here. Do we know anymore about how the USN 25%, or 23.5% rule was arrived at?

Did the industry, as Luxfer suggests, just grab onto an OSHA rule designed only for commercial divers.

Maybe. Has it proven a poor choice?

We presume, or at least hope, that the rule was not arrived at based solely on anecdotal evidence, but that is all we use to defend it when presented with a different standard used by several different groups without knowing how they selected their standard.

You may hope or presume, I have much less faith in regulatory bodies as a whole.

If the lack of accidents is sufficient, then we should not retro fit buildings for earthquake safety. Afterall, there are a lot of very old buildings that have survived a lot of earthquakes that are not up to code. If they did not fall down in the last earthquake, they must be safe enough.

Every choice should have a cost vs benefit analysis, or risk vs reward analysis. Should we mandate every building be retrofit? Sounds good until you look at where else that money could be spent. Would the greater good be served by retrofitting every building, or maybe it would be better to retrofit hospitals, fire stations, and stadiums, and spend the rest of the money on preventitive health care.....

Recreational use of Nitrox involves the same type of analysis. There is some increased risk of death and injury from the preparation of Nitrox. It's small IMO, but clearly not zero. There is a well known operational risk from the use of Nitrox, CNS tox etc.

This has to be balanced against the benefits, i.e. less exposure to Nitrogen. For the trained diver it's well worth it, in my opinion.


Tobin

 

[cool_hardware52]

I agree that the prudent thing to do is, on an industry-wide basis, greatly reduce the introduction of lubricant into compressed gases (including air) used by divers. Nitrox is no longer an exotic gas mixture. Given the wide incidence of real DCS and wider precautionary treatment for suspected DCS, moving toward even wider adoption of nitrox as a dive gas of choice is inevitable. These things reach a tipping point. Once most dive boats and dive shops offer nitrox fills an operation that does not provide that option is starting to look vulnerable when a recreational diver patron suffers DCS.

When I took the basic PADI course I got the sense that dive computers were exotic items carried by technical divers or gadget freaks (i.e., guys like me). Instead I can not remember anytime I've been on a dive boat in SoCal where a cetified diver was using tables (except, in theory, my wife - before I upgraded and gave her my old one). Nitrox is going to be the same way when it reaches the tipping point. People will dive Nitrox even with 3 dive 40 ft. 60 min. profiles because it gives them a safety margin or because they feel better using it. Sure you have to pay for it but you've already put down $120 to get on the boat and the price of nitrox will drop.

My point? When 2/3 of all active divers in the US are using nitrox some of the time and 1/2 are using nitrox all of the time the default for all tanks will be nitrox service, and air compressors that possibly introduce lubricants to the tanks will have to be replaced.

Jim

I agree. I think there will be a time where diving air will seem an unnecessary risk. Some think so today.....


Tobin

 

[Frank O]

When I took the basic PADI course I got the sense that dive computers were exotic items carried by technical divers or gadget freaks (i.e., guys like me). Instead I can not remember anytime I've been on a dive boat in SoCal where a cetified diver was using tables (except, in theory, my wife - before I upgraded and gave her my old one).

Um, er, any number of us here use "the computer in our heads" in conjunction with a bottom timer in gauge mode, but that's a different discussion ....

Two more things I wanted to add to this thread before I bail again. First, I thought it strange that when Luxfer listed the entities that endorse the 40% threshold, they overlooked a biggie (and, in the diving world, arguably the early prime mover) -- NOAA. This federal agency developed guidelines for nitrox use in the 1970s, and my recent edition of the NOAA Diving Manual shows they still stand by the 40% threshold.

Second, in looking around for info I came across a thread on the Deco Stop that has additional interesting background. I suspect there's something there for each of us to view as backing up our position:

Deco Stop thread from December 2004 on 23.5% vs. 40%

Once again, over and out ....

 

[drbill]

Perhaps you predictions will come true. I'm sure the majority of the divers dive multi-tank profiles that would let them benefit from the extra margin of Nitrox.

For others, like myself, Nitrox is an added safety risk since it limits my depth range on individual dives. While I am working on Nitrox certification, I will undoubtedly have to go to mixed gasses for some of the deep diving I do and remain with air for most of the rest.

How did this thread re: the Dive Park become so focused on Nitrox?

 

[jetfixer]

Maybe this thread could be split?

 

[LAJim]

Its really drifted some but there has been interesting discussion. My comments about "universal" use of computers and (in the future) nitrox obviously apply to divers who dive frequently and within recreational limits and not deep dives where air (or trimix) is used to keep pO2 under, say, 1.4 atm and/or the "computer" generates the dive plan at home to be executed in gague mode in the water.

Imagine this: in a few years most recreational divers are using nitrox. A diver who uses 21% and doesn't have a computer shows up on the boat and needs to be buddied up. Now, we know that a lot of recreational divers who are diving tables don't really plan or execute their dives on the tables. They buddy up with someone who is on a computer or they otherwise dive more or less the same profile as everyone else on the boat. The stay out of trouble because the boat enforces surface intervals and picks dive sites that tend to keep everyone within their NDL over the course of the day. But all of the nitrox divers on the boat want a short surface interval, because they don't have much residual nitrogen, and this guy's dive buddy for the day has his computer set to nitrox, so following his profile may not be very smart. Now its at the tipping point - and the boat suddenly doesn't welcome this guy's business until he switches to nitrox - and necessarily dives his own computer.

 

[scjoe]

Cool Hardware52,

You obviously seem to be looking to argue more than discuss. I am not sure what my Nitrox course has to do with the reference to a direct quote from an industry safety page that is at odds with your position that a mere 12% increase is not an issue.

You are correct that agendas creep into the forumlation of laws. Don't they also creep into the agendas of the dive industry or is that industry fundamentally different from the oil industry, automotive industry, tobacco industry etc.?

I don't see how it was presumptiuos of me to correctly state that, as you admit after harranging me, your training did not delve into how the different standards were arrived at. In that respect, it was limited just like everyone else's was.

The lack of accidents at 40% is one data point, but it is not test data and it is not a data point that tells you what can happen at various mixes under certain circumstances. That is what lab tests are for. If you found that in a lab at 25% you had a serious risk of fire would ignore it just because there was a lack of accidents at 40%?

I disagree that the cigarette smoking example was a red herring. The lying you are referring to had more to do with addiction, nicotine content and marketing, not underlying causes of cancer. Even then the lying was not discovered for years, so how do you know without the benefit of hindsight who is right about a particular standard at this point in time?

When you state that you don't think anyone is lying about Nitrox in order to set lower limits, I assume you meant higher limits. The groups you assume are acting with hidden agendas are the ones with lower limits.

Your statement that I may hope or presume, but that you have much less faith in regulatory bodies is out of context with the quote from my prior post. I was referring to the hope or presumption that the agencies you have chosen to place 100% trust in did not base their recommendation solely on anecdotal evidence.

Finally, my point about retro fitting was not that every building should be retro fitted but that buildings that do not fall down in an earthquake are not necessarily safe. Lack of collapse does not equal safety. Lack of history of fire at 40% does not equal lack of increased risk of fire. That is the problem with anecdotal evidence.

You are correct that a cost benefit analysis does take place, but it is a whole lot different to decide not to require a building owner to retrofit a small building when the cost may end his livelihood than to tell someone engaged in a sport that they have to spend more money to engage in one aspect of that sport.

That is where there may be a dive industry agenda coming into play. The compressed gas people are concerned about workers' comp claims or injuries to third parties. Their standards do not effect sales because the demand for their products is largely not optional. Their customers need the gas for their operations. They are not buying it for fun. The safety standards raise the price across the board from all suppliers and lower the risk of potential accidents and claims.

The dive industry is concerned about getting more people in the water, selling more classes, etc. They may feel that the more expensive it is (e.g., dedicated Nitrox tank), the more likely they will lose some customers.

This issue is really not between you and me. Neither one of us should have to provide evidence that either standard is correct. It is a problem caused by the dive industry. Instead of telling everyone there are different standards, they should justify from tests, not accident records, why theirs is safe, or they should at least tell us what the test results are along with the safety record. What does the test data show as the O2 percentage increases? What really bothers me is why the Navy went down to 25%. What caused that change?

Anyhow, its the weekend now and I'm going diving. I'll leave further discussion on this topic to others.

 

[drbill]

Cool Hardware52,
You obviously seem to be looking to argue more than discuss. I am not sure what my Nitrox course has to do with the reference to a direct quote from an industry safety page that is at odds with your position that a mere 12% increase is not an issue.

...I don't see how it was presumptiuos [sic] of me to correctly state that, as you admit after harranging me, your training did not delve into how the different standards were arrived at. In that respect, it was limited just like everyone else's was.

Hmmm... I guess it's all a matter of one's own perspective. I saw it the other way around, but that's just my perspective.