Nitrox Tank Marking

[scubadiver888]

@scubadiver888 how do you know that air fill invalidates the o2 cleaning?

Some of the places I've been to that do air fills only aren't filtering it to the same level as the places which do Nitrox. I don't know definitely that the air fill will invalidate the O2 clean.

However, I have known tanks which were supposed to be O2 clean but got air fills at questionable stations cause flash fires at shops which do partial pressure blending.

 

[scubadiver888]

you see green handles on O2 bottles on occasion, particularly on rebreathers. There is a trend now to start using red for suit inflation bottles that I imagine stems from argon generally being in a red bottle

I was lifeguarding at a pool recently and saw someone practicing with a slung oxygen bottle (I assume he was working on buoyancy, deployment, etc.) and it had a green handle. I've also seen shops with replacement handles for sale (black or green). It definitely seems to be a trend.

 

[hhmoore]

Hmm - just came across a pair of tanks locally... maybe I'll take this conversation seriously & snatch them up for air only use (and keep my nitrox tanks for nitrox only)

 

[scubadiver888]

@scubadiver888
There are 3 shops somewhat local to me. All have filled tanks for me (though, for convenience reasons, I generally split my business between two of them); and all of them know that I do air fills much of the time (maybe the previously mentioned 3/4 of the time was overly generous). None of them have suggested that it's an issue...if they had, I probably would have developed other habits. In fact, I questioned the place that did my nitrox course; and was told that if a place didn't want to do an air fill because of the nitrox sticker, I should go elsewhere. That same conversation included subsequent nitrox fills.
In my case, at least, nothing is hidden...and, if any of the shops involved voice a concern, I will designate tanks for nitrox or air; and remove the stickers, accordingly

Sorry, wasn't trying to accusing you of doing anything wrong. It is more that a lot of the people I dive with just didn't realize the potential danger of filling an O2 tank with air. Most the place I go have pretty clean air. If everyone was filling at these places then it is probably not an issue. For example, there are 5 shops approximate the same distance from me. All of them have air clean enough to do partial pressure blending. If I got my tank O2 cleaned then got air fills at any of these stations, I would feel pretty safe about my tank still being O2 clean over the next year.

However, my dive club goes to some places where the air isn't as clean and definitely not used for partial pressure blending. Often it is run by other scuba shops in remote locations; they only ever dive on air so being O2 clean isn't an issue for them. If I had an O2 clean tank and got it filled at one of these locations, I'd wonder about how clean it still is. Diving every weekend, I might use one of these "less than O2 clean" fill stations 16 to 24 times a year. Once or twice, probably not an issue. But you have a dozen divers with 2 tanks each doing this 20-ish times a year and that significantly increases the chance one of these tanks won't do well on a partial pressure fill.

I've mentioned this to people at my club and they just didn't think about it being an issue. They didn't do it on purpose. Rather than educate everyone on this, all the dive shops I frequent now use a stick, membrane or banked to do Nitrox. I think the last shop switch a few year back. If they need to do greater than 40% oyxgen it is for tec divers and they make sure tec divers never fill an oxygen bottle with less than O2 clean air.

I think it was @tbone1004 who was hinting that he doesn't know why everyone doesn't switch away from partial pressure blending.

 

[hhmoore]

I took as well intentioned, generalized criticism of a practice.
I didn't take it personally...but it does sort of give me a reason to consider purchasing two more hp100s.

 

[tbone1004]

@scubadiver888 correct, though it is slightly hypocritical as I PP blend most all of my tanks. I do that because I have free access to a fire department compressor quite literally across the street from where I work, that I obviously can't modify on the inlet side. It is far too convenient for me to take advantage of that vs. firing up my own compressor and/or going to another dive shop. I pump hundreds of cf/month vs. thousands though so it is inconsequential for that and my labor costs nothing.

 

[scubadiver888]

@scubadiver888 correct, though it is slightly hypocritical as I PP blend most all of my tanks. I do that because I have free access to a fire department compressor quite literally across the street from where I work, that I obviously can't modify on the inlet side. It is far too convenient for me to take advantage of that vs. firing up my own compressor and/or going to another dive shop. I pump hundreds of cf/month vs. thousands though so it is inconsequential for that and my labor costs nothing.

It is my understanding that once the tank is filled and the customer leaves with it there is no more worry than a tank filled with banked Nitrox. The real danger is when you are putting the oxygen in the tank. Since you are putting the oxygen in your tanks, you are taking the risk. If you are cool with it, I see no reason I should have a problem.

I know I'm pretty risk adverse. So I'd never do that. But that is just me. I also worry for my friends who fill tanks.

 

[tbone1004]

@scubadiver888 my objection with PP blending has nothing to do with safety. It's all a cost proposition. It is significantly more expensive to PP blend than it is to mix through the compressor

 

[scubadiver888]

@scubadiver888 my objection with PP blending has nothing to do with safety. It's all a cost proposition. It is significantly more expensive to PP blend than it is to mix through the compressor

Haha. I do this a lot. I was thinking about how you pointed out it is more cost effective to mix through the compressor rather than PP blending but when I wrote the message I didn't put that down. Thanks for clarifying.

 

[Brian Gronberg]

Seems like an odd response. How else would one know these tanks had Nitrox in them?

That's my thought too. It seems that just putting a piece of blue painters tape on them isn't the best solution.