Nitrox Is it customary to reanalyze it at the dive boat?

[MAGELLAN]

Thanks for the input. There went another 200 bucks, It's done. I wasn't implying I would not check it, really what I wanted to know is if it was common for the dive operation to offer Nitrox and then not provide an analyzer at the boat. Seems like they would to me. I was suprised when the operator suggested that since the tanks came from a certified mix station that I shouldn't worry about checking it. Oh well, that's Cozumel, right? I never really trust an operation 100% I like to check things for myself especially when my life is involved. Thanks for the replies

 

[DandyDon]

{Emphasis mine}

Thanks for the input. There went another 200 bucks, It's done. I wasn't implying I would not check it, really what I wanted to know is if it was common for the dive operation to offer Nitrox and then not provide an analyzer at the boat. Seems like they would to me. I was suprised when the operator suggested that since the tanks came from a certified mix station that I shouldn't worry about checking it. Oh well, that's Cozumel, right? I never really trust an operation 100% I like to check things for myself especially when my life is involved. Thanks for the replies

Ya' got that right. We gripe and poke fun at Lawyers, Insurnace Companies, Courts, and Government Regs here in the U.S., but when you leave - you leave protections we come to expect. I doubt that many U.S. operators would sell Nitrox without offering an analyzer, but elsewhere - who knows? And if a Gringo dies in the water, a medical expert can easily be obtained who will call it heart attack. Yes, I am exaggerating, but $200 is a small price for safety.

I have rethought my words since my first post. I'm buying one before I go south of the border again.

Oh yes, carry it in your roll-on luggage. You know that airlines are only liable for $9.07 a pound on checked luggage. Makes trip insurance even more inviting; I always do that for international trips, for several reasons.

 

[Diver0001]

I'm headed for a trip to Cozumel, and I wanted use Nitrox. This would be my first trip to use it, and when I asked about analyzing it at the boat, I was assured that it would be mixed by a certified center. My question is, after my recent Nitrox class, I felt we were supposed to reanalyze the tanks ourselves, isn't that customary? Do dive operators that provide Nitrox, also provide an analyzer, or... do you trust the mixer? We don't have one, obviously, and It's at least another 200 bucks to get one. I've already spent too much money just getting there, if you know what I mean Your thoughts please!

Never trust *anyone* to do this for you. I've ordered 32 and had it come out at 37 on the analyzer. He misread the order and thought I wanted 36. I even re-analyze buffered nitrox once it's in my tank. BTW you can buy a disposable O2 analyzer for a lot less than $200. Why don't you split the cost with a few other people on the boat and then draw straws to see who gets to take it home...... also there are about 10 thousand dive shops in Cozumel and you may even be able to rent one.....

R..

 

[MikeFerrara]

If you don't analyze your mix, you would be quite foolish. What happens if they put pure oxygen in your tank and you get to 70 feet? Mistakes happen to the best of us, and I wouldn't do a "trust me" dive on nitrox.

In fact, during last year's DEMA conference, a group of us went diving on a charter. We ordered 32%EAN in advance. When we got to the boat, our tanks were set up and marked 32%. We asked for an analyzer to check it, and were told they didn't have one on board and that the person who mixed them had been doing this for 15 years and was a nitrox instructor. This was not good enough for us, so we asked if we could take the tanks back to the shop to get analyzed. They said we could not, because there was no time. We started to pack up our bags to leave, and, fortunately, one of the other divers told us he had an analyzer in his car. We got it, and the dive was saved. PS-all tanks analyzed close to 36 percent, not the 32 we requested and was marked on the tank.

Don't put your life on the line for something as simple as an analysis.

I always have an analyzer with me (or at least in the group).

I think it's best to analyze your gas even if you ask for air. You never know.

 

[Sideband]

This is a trick question, right?
I calibrate mine before every use by removing the cap from the sensor and waiving it around in the ambient air.

Ideally, additional checks on 100% O2 and 100% Helium are a nice check on the condition of your sensor.

In our class we were told that the flow rate of the calibration should to be the same as the flow rate of the test. May be different with different meters but that is in my nitrox workbook as well.

Joe

 

[RichLockyer]

I was down in Curacao and had my tank fill by Ocean Encounters. I told them I wanted EAN32, I checked the 2 tanks and found the % was 24% and 26%. ALWAYS CHECK!

One of the locals out here took his doubles and an AL40 in for fills. He requested EAN50 in the AL40 and 21/35 (trimix) in the doubles.

When he picked them up, he found the isolator valve closed.
Suspicious, he analyzed each tank separately. The mixer had given him AIR in one tank and EAN35 in the other... no helium in either mix.

 

[Albion]

there was a case on here recently of a course in czech or poland (some hwere eastern europe and i wont mention the agency for fear of getting bashed ) but the long and short of it was that one of the students (actually an instructor) had mixed the gasses the night before and said they didnt need analising!!!! Post dive the senior instructor analised the gas back at the shop and found Very high O2 content. Luckily the training had been conducted shallow. When they were filled the guy had put in the O2 but forgot to top up with air. Cant trust anyone to fill the tanks correctly not even yoursself it can go wrong all too easily

 

[DORSETBOY]

that's bloody scary Albion, deff agree with you when you say to analize your own tanks.. dont let anyone pressurize you into not doing it yourself, it litterally takes seconds for anyone to do.

 

[miketsp]

In our class we were told that the flow rate of the calibration should to be the same as the flow rate of the test. May be different with different meters but that is in my nitrox workbook as well.

Joe

I understood that O2 sensors are sensitive to PP% but the construction of the sensor head is such that the reading is taken at very close to ambient pressure. The gas under test just flows across the sensor. So calibrating at ambient pressure is correct and sufficient. Altering the flow rate should have no significant effect.

The idea of having a cylinder of air to calibrate the sensor just adds another unknown variable.

 

[matt_unique]

One of the locals out here took his doubles and an AL40 in for fills. He requested EAN50 in the AL40 and 21/35 (trimix) in the doubles.

When he picked them up, he found the isolator valve closed.
Suspicious, he analyzed each tank separately. The mixer had given him AIR in one tank and EAN35 in the other... no helium in either mix.

When I get fills I basically do everything except connect the whip. I blast a little air out of the valves to clear any dust, I open my isolator, and I properly hoist them into the water tank. My first time I let the shop guy do it and of course they reach for the center of the manifold and they are not sure which direction is 'open' on the left post. I stay right there to watch the pressure, fill rate, and temp of my tanks. After they disconnect the whip I lift them out of the water tank. With Nitrox I usually have to leave them but the two people who do my Nitrox fills are very experienced and I have seen them handle everything properly.

--Matt