Nitrox question

[stuartv]

Do you think that people should always analyze their gas no matter what they "think" is in the bottle?

Yes.

Do you think that people should trust the accuracy of an unknown analyzer?

If it appears to calibrate to Air correctly and it analyzes the gas to the expected value (and which is 40% or less), I would generally trust it. But, I would always advocate being situationally aware and using good judgment. For example, if it's a reputable shop that looks clean and well-organized, and they offer a banked gas, and the analyzer they provide me is not the same one they use back at their fill station, then I would have no issue trusting their "unknown" analyzer. OTOH, if, for example, they are doing partial pressure blending and the analyzer they are offering for me to use is the same analyzer they used to do the mixing, then I might look for alternatives. In that situation, there's no way to know if their analyzer has an old O2 sensor that is reading low.

That's one reason why I carry my own analyzer with me and I check the calibration against O2 periodically.

The other reason is because I was diving in Hawaii once and the shop I booked a boat through met me at the boat with my tanks of Nitrox. They didn't bring an analyzer and the boat didn't have one (and I didn't have one yet). So, my choice was to trust their tanks or use other tanks they told me were air. I used the tanks of air (which, of course, still involved a level of trust).

 

[MaxBottomtime]

Well that also tells me that if they do not frequently check their own tanks that they also do not change their computer. You more than likely had people diving Nitrox on that boat and using Air on their computers, while there is nothing wrong with that. I would not do it.

Unless you have a PFO or are at a higher risk for DCS it makes no sense to set your computer for anything but the gas you are using. It doesn't make you any safer statistically and if you ever had to go to a chamber they would want to see your computer.

 

[stuartv]

Unless you have a PFO or are at a higher risk for DCS it makes no sense to set your computer for anything but the gas you are using. It doesn't make you any safer statistically and if you ever had to go to a chamber they would want to see your computer.

Even if you have PFO, the only time I think it makes sense to "game" your computer is if you are using a computer that doesn't have any kind of conservatism setting/adjustment. If it does, then I think you should use that to make your computer more conservative - not diving nitrox and set your computer to air.

 

[Doby45]

As I stated, I would not do it. But, I have seen it done more times than I have fingers on hands. I also am not going to "confront" someone that wants to dive that way. I think the practice is more common based upon my initial comments, people are too lazy to change their computers or they have forgotten how to.

 

[Jim Lapenta]

I analyze every tank. Every time. There are some shops in my area that do not pump nitrox. Ever. The demand is not there so they don't bother doing it.
The shop I work with does and being busy means there is the possibility that one of my cylinders may contain something other than air.
I also analyze for CO. Takes all of another 30 seconds to do.
Every nitrox class I have ever heard of requires students to analyze their own cylinders. Shops are supposed to ensure that anyone diving nitrox analyzes their own gas. Not watch the instructor, guide, fill guy, etc. do it. If the shop has an analyzer the diver is not familiar with then the shop shows the diver how that analyzer works, shows them how to calibrate it, then lets the diver calibrate it and do their own analysis. They then sign a log and apply some type of contents label on the tank.
Any instructor or shop that doesn't do this is stupid. As well as dangerous.
It is never the responsibility of the filler or the shop to do the FINAL analysis. That is solely up to the diver.
That was communicated even more clearly in my TriMix blender class this past weekend.

As an FYI, even if you rarely use nitrox it's a good cert to have. The additional knowledge won't hurt. When I do the hands on portion for an e learning student I charge 40 bucks. That covers the cost of the cylinders of nitrox I have to have and the certification fee I have to send to SDI/TDI. It also covers the cost of the analyzers I've had to buy and maintain. They don't just fall out of the sky.

 

[Lorenzoid]

I have been on at least one boat where the shop brought tanks and had them on the boat for everyone. Almost everyone was diving nitrox. I think I was the only one that asked for an analyzer and analyzed my tanks. After I did mine, I saw a couple of people then ask to use the analyzer and check theirs, but the way it all went down made me feel pretty strongly that if I hadn't asked, nobody else would have, either.
. . .

I guess this kind of thing goes on, but I haven't experienced it. When I have been on a boat where they brought shop tanks aboard for us, the DM passed around an analyzer.

Complacency lives.

 

[DandyDon]

Do you think that people should always analyze their gas no matter what they "think" is in the bottle?
Do you think that people should trust the accuracy of an unknown analyzer?

It strikes me as off that we only analyze cylinders when we think we have to, rather than uniformly at all times. And it strikes me as very odd that generally speaking we only analyze the o2/He content and are totally trusting that the shop who we don't trust to give us the mix we want have not made other mistakes which could have horrendous consequences. Why don't we ask for service records from the compressor and carbon monoxide readings before accepting gas?

I've seen divers go deep on nitrox tanks they thought were air, and I have seen non-fatal but scary carbon monoxide hits. My CooTwo tests for O2 and CO, and it's so easy to use. I test every tank.

 

[abnfrog]

jim as usual you are 105 % right I always analyze and if I don't know the shop (other than mine ) I check the co ..my life and my students lives are worth the cost . I don't have to bring up the Carlos F death to hammer that fact into my students DONT TRUST ANYONE EVEN ME to analyze your tanks do it yourself EVERY time ............just my 2 cents

 

[USMC CPL.]

I have been on at least one boat where the shop brought tanks and had them on the boat for everyone. Almost everyone was diving nitrox. I think I was the only one that asked for an analyzer and analyzed my tanks. After I did mine, I saw a couple of people then ask to use the analyzer and check theirs, but the way it all went down made me feel pretty strongly that if I hadn't asked, nobody else would have, either.

Which is to say that I think it's very real that some people learn stuff and assume that nobody bothers in the real world. So, you end up with a boat full of people who all look around and all think the same thing and nobody does it. And maybe the new guy on the boat wants to ask for an analyzer but is afraid to look like a greenhorn by asking when nobody else seems to care.

So, I totally agree with you that every instructor should look every student in the eye and tell them DO IT EVERY TIME! Do NOT be intimidated by others who seem to think it's not important. Do NOT be intimidated by shop employees or boat crew whom you are worried about "bugging".

And if you buy and carry your own analyzer, you'll never have to worry about it....

I have been on at least one boat where the shop brought tanks and had them on the boat for everyone. Almost everyone was diving nitrox. I think I was the only one that asked for an analyzer and analyzed my tanks. After I did mine, I saw a couple of people then ask to use the analyzer and check theirs, but the way it all went down made me feel pretty strongly that if I hadn't asked, nobody else would have, either.

Which is to say that I think it's very real that some people learn stuff and assume that nobody bothers in the real world. So, you end up with a boat full of people who all look around and all think the same thing and nobody does it. And maybe the new guy on the boat wants to ask for an analyzer but is afraid to look like a greenhorn by asking when nobody else seems to care.

So, I totally agree with you that every instructor should look every student in the eye and tell them DO IT EVERY TIME! Do NOT be intimidated by others who seem to think it's not important. Do NOT be intimidated by shop employees or boat crew whom you are worried about "bugging".

And if you buy and carry your own analyzer, you'll never have to worry about it....

I have been on at least one boat where the shop brought tanks and had them on the boat for everyone. Almost everyone was diving nitrox. I think I was the only one that asked for an analyzer and analyzed my tanks. After I did mine, I saw a couple of people then ask to use the analyzer and check theirs, but the way it all went down made me feel pretty strongly that if I hadn't asked, nobody else would have, either.

Which is to say that I think it's very real that some people learn stuff and assume that nobody bothers in the real world. So, you end up with a boat full of people who all look around and all think the same thing and nobody does it. And maybe the new guy on the boat wants to ask for an analyzer but is afraid to look like a greenhorn by asking when nobody else seems to care.

So, I totally agree with you that every instructor should look every student in the eye and tell them DO IT EVERY TIME! Do NOT be intimidated by others who seem to think it's not important. Do NOT be intimidated by shop employees or boat crew whom you are worried about "bugging".

And if you buy and carry your own analyzer, you'll never have to worry about it....

My lds insists that I come back to the fill station with them while they are filling my nitrox order and analyze it.

 

[stuartv]

Most shops I've been to won't let customers in the area where the fill station is.

One of my local shops does require me to analyze my tanks and fill out a line on a log. The other doesn't really seem to care whether I analyze or not. I always analyze, but they don't ask me to write anything in a log.