Nitrox BCD Question

[DennisC]

That may be true, but I think I was just confused between getting your tank cleaned and your gear. I probably could have just looked in my SSI book, but I'm lazy lol Thanks again

 

[Glenn08]

I considered trying Nitrox, but changed my mind when the dive shop told me that I would have to use only Nitrox, or get my equipment re-cleaned after using un-enriched air. I wasn't THAT interested.

 

[boulderjohn]

I considered trying Nitrox, but changed my mind when the dive shop told me that I would have to use only Nitrox, or get my equipment re-cleaned after using un-enriched air. I wasn't THAT interested.

That is why DennisC should not feel bad about being confused. A lot of people are greatly misinformed about this topic. Much in the way of course material is incorrect, and many instructors are poorly informed. He may well have been given bad advice, just as you were.

Your dive shop was dead wrong, and you should consider finding one that knows what they are talking about. Read what kotik wrote very carefully--what he said is correct, but you have to read what he said precisely.

First of all, many shops and many individuals still use partial pressure blending. I am one of them, and I have done it a lot. Think about what happens in partial pressure blending of nitrox, and then realize what a total crock of caca your shop fed you.

1. Step 1 of partial pressure blending: the blender adds pure oxygen to the tank. That is why the tank needs to be O2 cleaned.

2. Step 2 of partial pressure blending: the blender hooks the tank up to the compressor and fills the tank the rest the way with air.

Whether you get a nitrox fill through partial pressure or get air instead, your tank is going to have air put in it from the same compressor.

People who fill tanks that have the potential for partial pressure blending should be using highly filtered air that is safe for such use. Its potential for contamination is the same whether they put O2 in first for nitrox or just add the air to the empty tank.

 

[Zung]

Not only the shops; the regulatory guys also try to get at your wallet. Anybody knows about that M26 abomination? It's still actual, but the community chose the right way to deal with it: just ignore it, it'll not go away, but the harm is contained.

 

[kotik]

Not only the shops; the regulatory guys also try to get at your wallet. Anybody knows about that M26 abomination? It's still actual, but the community chose the right way to deal with it: just ignore it, it'll not go away, but the harm is contained.

I don't know much about the situation in Europe... just a vague recollection of a proposed law to require special Nitrox-only tanks outfitted with a valve that only matches dedicated "Nitrox" regulators. I thought that never passed into law. Am I reading your post correctly that this is the case, that it was rejected?

I'd have to say I'm fairly insulated in the world of the Americas. Here, we have some dive destinations where we just wish the locals were more careful about getting exhaust fumes in the fills.

 

[halocline]

All will become clear when you take your Nitrox course,

If only that were true. Agencies and shops seem to be fairly confused regarding equipment protocols for recreational nitrox, with lots of mention of 'nitrox clean' and 'nitrox regulators' and the various scenarios in which O2 clean is necessary for gear. You see statements floating around about the CGA (or some gas authority) recommending O2 protocols for anything over 23% O2, I have no idea if that's true, half-true, or outright fabrication, and each shop seems to their own ideas about what's 'correct.' Don't forget, the nitrox courses are typically taught by the very same people that are making up these rules at the shops.

Add that to the fact that at least two of the regulator manufacturers, atomic and scubapro, have released somewhat complicated legalese-esque policies about nitrox with titanium regulators. It's very easy to get confused.

Now, if in fact, as some polices imply, regulators 'should' be O2 cleaned for nitrox use, then in fact it would be appropriate to require the same of BC inflator valves hoses, and bladders. It's the same gas, and there's WAY more combustible material. How about drysuits? It's a slippery slope when you start talking about nitrox as being handled like pure O2.

And I am fairly certain that this is all 'fueled' (no pun intended) by one big magic word; money. The dive industry now relies on nitrox use in recreational diving; they want to make it as accessible as possible, and they would like to be able to generate revenue in as many ways as possible. Hence the less-than-forthwright "nitrox" version of the MK20; a blatant money-grab by SP. But, push the rules for special handling and gear requirements too far, and poof; it's a technical diving thing and there goes the big market. Meanwhile, there are actual concerns for safety. An O2 fire is a very nasty thing, regardless of the remote chances of it occurring in nitrox use.

The 'simplest' and generally accepted policy taught by the agencies is that anything exposed to 41% or higher needs to be O2 cleaned, and that's what most people will quote. This basically keeps O2 cleaning in the realm of technical diving, except for tanks filled with partial pressure blending, and by some stunning coincidence, keeps recreational nitrox as 40% or lower.

The oddball thing is that exactly what constitutes "O2 clean" and how to maintain it is likewise not clear. Hence the reference to not being able to use 'regular' scuba air in a tank that's O2 clean. That's only true if the air is not modified grade E, i.e not filtered to the same standard as air used in partial pressure blending. And of course there's a great deal of trust involved; trust that every single fill on a given tank is truly up to clean standards, for example.

And yet, somehow thousands of nitrox dives take place world-wide every day and you don't hear about tanks exploding or BCs bursting into flames.

 

[Zung]

... I thought that never passed into law. Am I reading your post correctly that this is the case, that it was rejected?...

It's a standard, just another DIN, not a law. Even though it's passed as a standard, any law abiding citizen can safely choose to ignore it.

 

[Nemrod]

I have yet to see a BC spontaneously combust, so, I doubt you have anything to worry about. In fact, I am very sure that I am O2 clean, well, if I catch on fire at least I will be underwater and hopefully will not combust for too very long.

N

 

[Zung]

So the correct procedure would be:

1. Deflate BCD
2. Jump
3. Assess BCD is fully immerged
4. Inflate BCD

Correct?

 

[halocline]

Yet another example of BP/W superiority over jacket BCs. With the BP/W, you have a steel heat shield between you and the burning wing, where with the full-wrap around bladder of the jacket BC, you're toasted in no time.