Catalina U/W park dive report.

[drbill]

Maybe this thread could be split?

Seems like an appropriate move to me. Mods?

 

[limeyx]

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


Tobin

Sadly in Southern California, its pretty hard to find a boat that fills Nitrox.

I dive nitrox almost all the time. The exception being really shallow beach dives, or shallow practice, and boats where it isnt possible to get nitrox fills (for 2nd, 3rd dives etc.) If I got a 1/2 price nitrox fill for topping up 1/2 full sets of doubles, I'd use it even more.

 

[cool_hardware52]

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.?

The dive industry is actually a pretty good example of successful self policing. The VIP policies are voluntary, and have proven very successful in effectively removing dangerous tanks from service, so much so that Feds do not yet see the need to codify the VIP system with law. If tanks were blowing up every day I'd bet you'd see a federal law mandating inspections. To imply that the dive industry is the problem, and that it promotes inherently risky handling of O2 is at odds with this demonstrated self interest in safety.

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.

You stated that there was no meaningful discussion of different standards, that does not describe my classes accurately.

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%?

If a car crash at 40 miles per hour is surviable, it's fair to assume that a crash at 25 mph will be if anything less severe. I'm quite confident that there is copious data to show an increasing risk with increased O2 fraction and or PP.

What I do know is that 100% O2 use in scuba has resulted in dramatic events, and 40% and down apparently has not. That at least suggests that lower fractions are less risky.

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.

I make no assumptions about hidden agendas. If I had to guess the lower 23.5% limits were likely set with no thought or regard for it's impact on scuba. What exactly is there to lie about? All the 32% bottles that exploded and were covered up?

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 think I was pretty clear. In a perfect world standards would be set based on review of the risk. This is seldom the case in the real world.

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.

Damn few thing I trust 100%, I make a risk / reward analysis. In the absense of test data this analysis will be on the available evidence, even if anecdotal.

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.

That's not necessarily true. Why didn't that specific building collapse? Was it chance, or was there something about it's orientation, or natural frequency, or mass, or the underlying strata that we don't yet understand. That some fell and others did not should be examined.

Building codes are a perfect example of how not to regulate. Building codes have to be simple enough that they can be applied to a huge range of applications, and inspected in the field for compliance, often by poorly trained people. What results is "cookbook" enginneering, i.e. so many nails per foot, etc. This done so the carpenter in the field has a "standard" he can understand, and the Building Official can check his work with nothing more than a tape measure. It works, but in virtually every case the structure is over built.

Th equivalent in the compressed gas world would be "any O2 percentage greater than air requires O2 service" 23.5% is effectively exactly that, the 3.6% difference is likely just to allow for instrument error in analyzing the gas.

Lack of history of fire at 40% does not equal lack of increased risk of fire.

There is likely an increased risk at 40% over 23.5%, or 25%. A lack of accidents over a long period, and untold number of fills does indicate that the increase in risk is still very low and within acceptable range.

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.

So we don't want to end the building owners livelyhood arbitraily, but it's ok to impact the economics of the scuba business?

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.

It just raises costs and shifts the risk.

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.

More cost usually means fewer customers. If those costs are due to unneccessary regulation of course they will and should be opposed.

This issue is really not between you and me. Neither one of us should have to provide evidence that either standard is correct.

Full agreement up to here.

It is a problem caused by the dive industry.

What problem? Show me the bodies!

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.[/QUOTE]

Do you suspect that there is a industry wide conspriacy to with hold damaging test data? My guess is the data doesn't exist.

What really bothers me is why the Navy went down to 25%. What caused that change?

This is only my speculation. What sort of environments, or processes involve elevated O2 percentages? Those where O2 is intentionally introduced. How well can you control the introduction of this "extra" O2? Is it possible that you may have created a much higher concentration and not know it? While this is not a concern for membrane nitrox system, it could well be for the USN.

One way to limit risk is to set a very low O2 limit for requiring O2 service. That way if you accidentally exceed it your still marginally safer. In other words the low limit may reflect operational imperfections in controlling O2 percentage, and not the risk directly associated with mixes from 21-40%.

Consider this, if the USN required every compressed gas system to be prepped for O2 service, then they need not worry at all about controlling the actual percentage. Great if you have a ready tap on the US treasury, not so good for the rest of us.

Anyhow, its the weekend now and I'm going diving.

Have fun, dive safe,


Tobin

 

[PhotoTJ]

Sadly in Southern California, its pretty hard to find a boat that fills Nitrox.

Off the top of my head, the Peace, and the Great White both fill nitrox.

 

[double80s]

Sea Bass, Sand Dollar

 

[Makin Raider]

Gotta catch the Sand Dollar soon though, I heard she's on her way to HI.

 

[IceDiverInCA]

Add Psalty V, Second Stage, Pacific Star and Lois Ann to the list.

I guess nitrox is far more interesting to talk about than the service in Avalon.

 

[drbill]

This is going a long way away from the Catalina dive park! However it is interesting.

 

[PhotoTJ]

*AHEM*

I have always gotten pretty good service at the dive park. Not perfect, (kids, after all!), but good enough.

There, back on track!

 

[limeyx]

Add Psalty V, Second Stage, Pacific Star and Lois Ann to the list.

I guess nitrox is far more interesting to talk about than the service in Avalon.

Still, I think more boats dont have it than do. I love the peace, and have used sand dollar and sea bass. However, on Peace for sure, the times I have used it probably 5-7 people out of 30 were using nitrox (usually shallow diving at anacapa but I still like to use 32%) I guess that makes it hard to make your investment back.

And I do agree with others in the thread that liability is a huge issue these days, and that stores even if some want to be more flexible just cant take the risk of a multimillion dollar lawsuit. My store doesn't require O2 cleaning for 40% fills, or the huge nitrox bands that (as MHK pointed out) basically serve no useful purpose.

My tanks however, are O2 clean, I just dont necessarily (as Frank O points out) consider a non-o2-clean air fill to magically invalidate that. Probably more significant is the tank being left in my garage for x months without being dives, picking up exhaust from car exhaust, or getting sand in it from beach diving.

if you are partial pressure filling, or using pure O2, I do think you need to be more careful.