Should I buy a nitrox (O2) analyzer?

[Centrals]

I have never ever came across any operators in SE Asia that did not require their customers to analyse the nitrox tank themselves.

 

[Diverlady13]

The clues you've dropped lead me to believe I have a good idea of the dive op you're referring to. If I'm right, I've dove with them quite a bit and never had a problem like the one you describe. In fact, we started diving with them years ago when they were a relatively small operation in south Florida.

If I'm right, then I agree with you: the owner and his QC staff would really like to hear about your experience. If you want to PM me the name of the op, I am curious to find out if I'm right.

Thanks. I don't want to call a reputable business out in the forums, at least not before I've addressed the issues directly. The customer service was mostly good with a couple of notable exceptions. That I can easily let pass because nobody is perfect 100% of the time. There was one dive in particular that really was total chaos at the surface and someone could have been badly hurt - or worse. I guess that does warrant a letter because it was a situation that was totally avoidable. Funny thing was that if the crew had followed the captain's instructions for entering the water, that dive would have gone smoothly despite the very rough water that day.

 

[yle]

Not sure how common this is, since I have only been on one dive boat, but I did the advanced and Nitrox courses about a month ago. The boat we were on did not pass around an O2 analyzer or even have the tanks labeled. The captain just carried your 2 tanks on board and said "31% and 32%" and that was it.

How common is it? I have never seen it, and I would not use an operator like that again.

It seems to depend on geography. In the USA, it's been my experience that dive shops providing nitrox typically have a logbook and insist their nitrox divers fill it out properly, including a signature. I'm in Cozumel right now and this week has been like every other I've spent here (with a variety of dive ops): if you want nitrox, they'll have it waiting on the boat and they'll even set up your gear for you and they pride themselves on their service, including the assurance that your 32% nitrox tank actually has 32% nitrox. It's definitely a BYOA kind of place, and when I pull out my analyzer I explain (to avoid hurt feelings) that I'm a "trust, but verify" kind of person.

Caveat: my experience is pretty limited, both in the USA and beyond. I just wanted to add the perspective that both ends of the "users analyze their own nitrox" spectrum of expectation do exist, so if you travel you could run into anything on this spectrum. Take care of yourself, have your own analyzer.

 

[Centrals]

I have no intention to buy an analyzer.
And if I cannot analyse the nitrox tank that I was given to dive, I will not use it. Period.
I do not mind to analyse the tank the day/night before in the shop or filling station but I must be able to verify the content myself. I will label the tank with my name, date and the the MOD of the mix.
My training from Day1 of my basic nitrox course yrs ago.

 

[Diverlady13]

Thanks everyone. I did go ahead and order an analyzer. I'm hoping it arrives before we leave next Saturday.

 

[Storker]

I have no intention to buy an analyzer.
And if I cannot analyse the nitrox tank that I was given to dive, I will not use it. Period.
I do not mind to analyse the tank the day/night before in the shop or filling station but I must be able to verify the content myself. I will label the tank with my name, date and the the MOD of the mix.
My training from Day1 of my basic nitrox course yrs ago.

I fill nitrox at my club. My club has a continuous nitrox system, so what goes into my tank is pretty well specified. Calculating the final mix is pretty easy. And then I analyze my tanks using my own analyzer before labelling them and storing them. When I'm gearing up, I analyze again. I have three data sets telling me what my mix is. If fewer than two of them agree I sit out the dive.

Analyzer cells die. You don't have good data telling you if your analysis numbers are good, or if they're corrupt. To quote Meat Loaf, two out of three ain't bad. And I'd hate seizing underwater because I messed up my analysis. A helicopter trip to the closest pot I can probably live well with. Seizing underwater... probably not so much.

 

[boulderjohn]

As we discuss the importance of analysis (and we should), I would like to make a couple of comments that may put some people at greater ease.

1. While you should certainly respect for standard MOD for your mix, you should also understand that it is not like you go below the MOD for a few seconds and then die. There is a time element involved, and it can be significant, although unpredictable. I know one person who took an O2 hit (and died) after spending more than 20 minutes below 150 feet on EANx 36.
2. Given the normal limits of recreational diving, it is unlikely that someone with an AL80 diving within recreational depth limits would ever be deep enough long enough to have a toxicity event, provided that the mix is within the 40% limit. I have been active on ScubaBoard for 17 years, and I don't ever remember an event being discussed in which that happened. I have on a couple occasions asked readers to provide any examples in their experience, with no results. The event mentioned in #1 was a technical dive, with the diver at that depth far longer than what could be done with a single AL80.
3. A DAN study on the supposed effects of Sudafed on oxygen toxicity gives an interesting take on this. They spend half the report talking about the lack of information on which to make a judgment; that is, they could not find clear cases of toxing events. The only cases they found in the literature were cases in which divers separated from buddies were found dead, with no clear reason. If they were using nitrox, well, maybe that was the reason. Maybe not. With no witnesses, they had no way of knowing. The case against using Sudafed was based on a few such examples.
4. I know of a number of toxicity events with technical dives, and in almost all cases, the divers were mistakenly using a totally inappropriate gas for that depth. One was the case in #1, where the diver assumed his doubles were filled with air and didn't check. In another case, a diver refused to check a tank that was clearly marked as having pure oxygen--he had filled the tank himself, and he knew it had plain old air in it. He breathed it for a while at 100 feet. It was pure oxygen. In another case, cave divers carrying multiple tanks were supposed to leave tanks with 50% oxygen at a 70 foot level to use for decompression on their return trip, but one of them left a deep mix bottle there instead and then went to 200 feet breathing the 50% mix, an inexcusable breach of technical diving protocols.

So, in summary, I always check the mix in my tanks, because that is where a problem will occur, but I don't sweat the difference in a percent or two for recreational dives. I respect standard MODs for the most part, but on recreational dives, I don't worry if circumstances make me violate it briefly. I am much more anal about MODs, mixes, (etc.) on technical dives--much more.

 

[Ayisha]

...In another case, a diver refused to check a tank that was clearly marked as having pure oxygen--he had filled the tank himself, and he knew it had plain old air in it. He breathed it for a while at 100 feet. It was pure oxygen...

Very close, 98% O2 with a seizure at 85 feet and PPO2 of about 3.5. It apparently happened pretty quickly, maybe in as little as 8 - 10 minutes, but that was an extremely high PPO2. Of course, we know it's a function of time at depth.

Definitely, we should always know what we're breathing.

 

[Centrals]

I fill nitrox at my club. My club has a continuous nitrox system, so what goes into my tank is pretty well specified. Calculating the final mix is pretty easy. And then I analyze my tanks using my own analyzer before labelling them and storing them. When I'm gearing up, I analyze again. I have three data sets telling me what my mix is. If fewer than two of them agree I sit out the dive.

Analyzer cells die. You don't have good data telling you if your analysis numbers are good, or if they're corrupt. To quote Meat Loaf, two out of three ain't bad. And I'd hate seizing underwater because I messed up my analysis. A helicopter trip to the closest pot I can probably live well with. Seizing underwater... probably not so much.

Your trust to your club is your own business but I would not use any nitrox tank that I have not analysed myself.
I have been using Nitrox since 1997 and never ever dived a nitrox tank without being analysed by myself first.
I have no control on others, just keep it simple.

 

[Manatee Diver]

Your trust to your club is your own business but I would not use any nitrox tank that I have not analysed myself.
I have been using Nitrox since 1997 and never ever dived a nitrox tank without being analysed by myself first.
I have no control on others, just keep it simple.

To trust you club isn't the point that he is making, but that you need to cross check to make sure that your analyzer is correct.