Analyzing your own nitrox tanks

[Synonymous]

I took the PADI nitrox course this week, and it was made very clear that you always analyze your own tanks before using them. Then I was told that the analyzers are very expensive and there is usually one around to use.

The next day I got on the boat with the same shop (my instructor was on board). I used their analyzer and got a very different reading from what was marked on the tanks. A crew member came to help me and it turned out the analyzer was drifting after being calibrated. After we tried a few times and got varying readings approaching what the markings said, she told me that it was okay to use the percent marked on the tank.

That night I met a local guide for a dive and she provided the nitrox tanks. She didn't have an analyzer so I went with what she had marked on the tanks.

It seems like many of the "rules" I've been taught in scuba courses tend to be more "guidelines" when I get out in the real world. Is this one of them? What are people's practices as far as analyzing your own tanks?

 

[scadreau]

I only say "Wow".

This is not the norm in any of the locations I have frequented. If the blend is much richer than is labeled and you don't analyze and find out, you may suffer a CNS hit. If it is much leaner than labeled and you do a bunch of diving, you risk a DCS hit. I have only been on one dive where I couldn't analyze my own tanks. The hard bottom was 60 feet and we were only doing two dives so we didn't have to worry about CNS (unless it was a crazy rich blend) and we dove air NDL's. I will never do it again for any reason.

You and only you can decide your risk tolerance. If you feel like the blender could not have mislabeled a tank and are willing to risk it, you can make that choice. I know I like being alive and uninjured a lot more than diving.

 

[JohnN]

I took the PADI nitrox course this week, and it was made very clear that you always analyze your own tanks before using them. Then I was told that the analyzers are very expensive and there is usually one around to use.

The next day I got on the boat with the same shop (my instructor was on board). I used their analyzer and got a very different reading from what was marked on the tanks. A crew member came to help me and it turned out the analyzer was drifting after being calibrated. After we tried a few times and got varying readings approaching what the markings said, she told me that it was okay to use the percent marked on the tank.

That night I met a local guide for a dive and she provided the nitrox tanks. She didn't have an analyzer so I went with what she had marked on the tanks.

It seems like many of the "rules" I've been taught in scuba courses tend to be more "guidelines" when I get out in the real world. Is this one of them? What are people's practices as far as analyzing your own tanks?

Very experienced divers have died diving mis-labled tanks. For $100 do you want to make it +1 ?

 

[Synonymous]

It sounds like a very common sense rule to me, I was taken aback to find it treated rather casually the very first times I dove nitrox after the training. I guess I should spring for my own analyzer.

 

[JohnN]

It sounds like a very common sense rule to me, I was taken aback to find it treated rather casually the very first times I dove nitrox after the training. I guess I should spring for my own analyzer.

I would walk away from a diver operator that did not make you analyze your tank and sign off before you took it from their shop or got on their boat

 

[Scared Silly]

The outfits seems to bending the rule to fit themselves. As said, experienced divers have died due to using mislabeled cylinders. My suggestion is to get your own analyzer so you are never in the position again. I have had mine own since day one.

 

[fish149]

There are a lot of folks out there who just go with the flow and ( god bless them ) trust others way too much. I went on a chartered dive once and when I arrived I asked where my tanks were so I could analyze them. The shop had already load them in the truck to run out to the boat. The dive master was very cool about it though and unloaded them then let me analyze them. He asked if I was military or tec diver cause those were the only ones who ever ask to analyse their own gas.
This is a simple thing you can check relatively easy.
Btw, I don't own an analyzer but I've never been anywhere where someone didn't have one. If I wasn't able to analyse I guess I just wouldn't dive.

 

[Steve_C]

Have an analyzer but usually use the shops or watch somebody analyze it in my presence. Never a question. Did run across a shop where the help tested a different tank and then calibrated for my tank in front of me by just resetting it to 21% without clearing the line. I told him that was not acceptable. I exposed it to air and then set to 21%. Turned out the mix was 3 % richer than what I had asked for. Had the shop reblend the mix. I also switched to a better shop. This one recalibrates to a tank of air before every measurement. They even have you measure when you buy a tank of air to make sure it is 21%. They get all my local business. Part of their caution is that one of management was once given a dangerously rich mix by a boat trying to be helpful and not knowing the intended use. (They thought a tank was a deco bottle but it was not)

 

[BRT]

You should not be calibrating an analyzer in between tanks. Just go tank to tank. We just spent three weeks in Quintana Roo and everybody was shocked when I wanted to analyze our tanks. They were okay with it, but surprised I wanted to.

 

[Steve_C]

You should not be calibrating an analyzer in between tanks. Just go tank to tank.

I assume that it was calibrated before the first tank and you know that no one has touched the calibration knob since then. I have picked an analyzer up and found that it was off.