Systematic use of oxygen analyzers by advanced divers ? [Poll].

[Caveeagle]

The historical baseline for tanks filled with air is really not relevant for (most) of today's divers. It was really not that long ago, that I got OW certified (1990), and PADI did not yet even recognize EAN/Nitrox as a safe recreational option for divers. Norms in diving are changing rapidly. I just has a conversation with the only LDS (I am aware of) within a 50mile radius that does not currently sell nitrox. And they are planning to add banked 32% soon.

 

[lv2dive]

You make a valid point, and I should have qualified my post. I’m not an instructor and the following is off the top of my head - so please forgive me if I missed something big (and take note of #4 ;-) )

I’ll accept there’s a greater risk diving with Nitrox vs air. The items are listed below are irrelevant as an air diver... they are exclusive to Nitrox (well, and trimix of course). Nitrox divers have to
A. Determine/adjust MOD (max operating depth) based on O2%
B. Respect the MOD during the dive (which is a changing number with Nitrox, with air your hard bottom is x depending on the partial pressure of O2 you’re comfortable with)

But some of the risks are there for Nitrox AND air. You can end up with a higher Or lower O2% in your tank than you realize, due to (including but not limited to)

1. Blending errors.
2. Wrong gas being put in the tank (if you own tanks) or getting a tank with the wrong mix
3. Grabbing//picking the wrong tank (tank has x and you thought it had y)
4. Etc

At the end of the day, the problem is that it’s not difficult to end up too much or too little O2, regardless if you are diving air or Nitrox. The risks are there. Too much O2: Oxygen toxicity. Too little O2: DCS (bc you stayed on the bottom longer than you should have with your mixture).

To get to your question (finally!), you are correct that this (not analyzing air) is not causing major problems left, right and center in the recreational world. I would not be surprised if the issues unique-to-Nitrox (A and B above) are responsible for more near misses and/or accidents than the risks related to air/Nitrox.

Howaever... when a tank has the wrong gas in it, it can be fatal QUICK. And, it just takes seconds to analyze your gas. So why not take those seconds to make sure?

Out of the millions of tanks filled with air around the world each year, what percentage do you think are accidentally filled with nitrox with no nitrox labeling etc on the tank? Serious question, because the overwhelming majority of divers out there have never analyzed a tank in their lives and I've seen zero dive shops that analyze each of their air fills to ensure they are actually air before giving them to those divers who are not going to analyze their tank. Despite all that "no checking air fills at all" I've yet to hear any statistics suggesting to me that all these people are taking huge risks because of the prevalence of this problem you've apparently seen. Even DAN doesn't seem to suggest we should check air fills for excess O2 (though they do recommend checking for CO or unusual odor/taste).

 

[vovanx]

I always test nitrox and almost never test air.

 

[Valyngar]

I try to test everytime, but some times there is no analyser at hand after top/refill. When this happens, I mark down pressure before fill/top up, %O2/HE (both for to be filled and top up tank) and pressure after top up/ fill. Then you can calculate new mix's o2/HE. I only do this for 1 top/fill max. Calculated % fall under 1% from measured.

 

[Akimbo]

For air, no

I'm an "other". I don't analyze when the fill system is air only or the depth is above the MOD for the banked Nitrox.

 

[tbone1004]

I can't vote for always because I do not always analyze. I most always analyze, but there are some exceptions.

I do not analyze my tanks most of the time when I'm teaching. I have a set of doubles that I use, that only I fill, only ever fill with air, and when I teach it is nonstop diving for ~2 weeks at a go. MOD on those dives is 40ft, I only fill from 2 compressors, neither of which has any ability to add anything other than ambient air, both of which have CO analyzers on them and auto-shutoffs for high CO *set to warn at 2ppm and cut off and 5ppm*. I analyze the tanks before the start of OWT just to make sure, but don't bother checking them in between.
If I'm diving with anything outside of air from those two compressors, in any other environment, I analyze every time. Not worth the risk.

 

[jlcnuke]

You make a valid point, and I should have qualified my post. I’m not an instructor and the following is off the top of my head - so please forgive me if I missed something big (and take note of #4 ;-) )

I’ll accept there’s a greater risk diving with Nitrox vs air. The items are listed below are irrelevant as an air diver... they are exclusive to Nitrox (well, and trimix of course). Nitrox divers have to
A. Determine/adjust MOD (max operating depth) based on O2%
B. Respect the MOD during the dive (which is a changing number with Nitrox, with air your hard bottom is x depending on the partial pressure of O2 you’re comfortable with)

But some of the risks are there for Nitrox AND air. You can end up with a higher Or lower O2% in your tank than you realize, due to (including but not limited to)

1. Blending errors.
2. Wrong gas being put in the tank (if you own tanks) or getting a tank with the wrong mix
3. Grabbing//picking the wrong tank (tank has x and you thought it had y)
4. Etc

At the end of the day, the problem is that it’s not difficult to end up too much or too little O2, regardless if you are diving air or Nitrox. The risks are there. Too much O2: Oxygen toxicity. Too little O2: DCS (bc you stayed on the bottom longer than you should have with your mixture).

To get to your question (finally!), you are correct that this (not analyzing air) is not causing major problems left, right and center in the recreational world. I would not be surprised if the issues unique-to-Nitrox (A and B above) are responsible for more near misses and/or accidents than the risks related to air/Nitrox.

Howaever... when a tank has the wrong gas in it, it can be fatal QUICK. And, it just takes seconds to analyze your gas. So why not take those seconds to make sure?

I agree, it takes seconds to analyze your gas.... if you happen to have an analyzer handy. To date, I have seen zero people use a personally owned tank analyzer. I've seen people who weren't willing to spend a few hundred dollars to own their own gear, but I haven't seen anyone spend the hundreds of dollars to buy their own analyzer. Personally, unless I was planning on routinely diving with gases other than air, I'd see no need to spend the hundreds of dollars on equipment to do the analyzing. If you have the equipment anyway, sure it doesn't hurt anything to check that the air in the tank is still air. Spending hundreds of dollars on a tool that is unlikely to find a problem when you're just diving air, in tanks not marked for anything else, from a professional dive shop seems a bit overly cautious to me though.

Sure, on nitrox I'm using the shops equipment and checking, but as a general rule I'm not taking the effort or spending the money. Someday I may switch to diving nitrox regularly, or tri-mix etc, and then I'll probably pick up an analyzer for convenience, and then it would probably be convenient to check anything, but for now it's an expense and effort I just don't see the need for as the odds of my tank of air having the wrong gas in it is exceptionally low imo.

 

[Gareth J]

Things for me changed when I switched to CCR. I generally fill my own O2 from my own J's. I generally pump my own Air, for the DIL. So I use my analyser less than I did when I dived OC.

However, I am part of a club, on any trip there will be a minimum of 3 analysers (personal equipment). Around a good half of the boat will probably be diving Nitrox, either back gas or stages. Other than those diving personal cylinders that are only filled with Air, everyone else will check their mixes with an analyser. even if they where previously checked and labeled.

No one should dive a cylinder that may, has had, or does have a mix in it without confirming the mix prior to fitting the regulators.
We can have mixes on board from 27% to 100%.

Currently my bailout is 21%. Sometimes its richer, a nice bailout mix is 27%, because that gives me easy flexibility to 40m.
Because I don't generally use the bailout, it doesn't change often. My two bailout cylinders are different and labeled with their current mix.

We often have custom mixes on board for specific dives. Or cylinders are air toped after a previous dive.

If you are using Nitrox, double check the mix before use. If you are using a cylinder that is not yours, that may have had a mix in it, double check it. It is unforgivable to use a cylinder with a mix in that you haven't double checked on the boat prior to fitting the regulators.

Part of the discipline does go back to the early days when we started using Nitrox. It was seriously discouraged. Some boats wouldn't accept Nitrox on board. So many cylinders where unmarked, and smuggled on board. Cylinders where always checked prior to fitting regulators - to confirm the contents.

In the 20+ years we have been using Nitrox, we have never had an accident in terms of a diver using the wrong mix, either rich or lean.

If you are not prepared to double check what is in the cylinder directly prior to use, you shouldn't be using Nitrox.

Gareth

 

[rjack321]

I agree, it takes seconds to analyze your gas.... if you happen to have an analyzer handy. To date, I have seen zero people use a personally owned tank analyzer. I've seen people who weren't willing to spend a few hundred dollars to own their own gear, but I haven't seen anyone spend the hundreds of dollars to buy their own analyzer. Personally, unless I was planning on routinely diving with gases other than air, I'd see no need to spend the hundreds of dollars on equipment to do the analyzing. If you have the equipment anyway, sure it doesn't hurt anything to check that the air in the tank is still air. Spending hundreds of dollars on a tool that is unlikely to find a problem when you're just diving air, in tanks not marked for anything else, from a professional dive shop seems a bit overly cautious to me though.

Sure, on nitrox I'm using the shops equipment and checking, but as a general rule I'm not taking the effort or spending the money. Someday I may switch to diving nitrox regularly, or tri-mix etc, and then I'll probably pick up an analyzer for convenience, and then it would probably be convenient to check anything, but for now it's an expense and effort I just don't see the need for as the odds of my tank of air having the wrong gas in it is exceptionally low imo.

I love answers like this...

1) CO is a lot more common than you think, especially in the tropics and hot conditions. 2) And I find it hilarious that you'll potentially spend thousands of dollars on gear and trimix training but a $150 O2 analyzer is just a silly convenience.

 

[hroark2112]

I brought my analyzer on a liveaboard because it’s just more convenient to have my own than to either wait for someone else to finish with the boats analyzer or to have someone waiting for me. Plus I have the adapt to the BC hose on mine so I don’t have to hold it in front of the opening. Just plug it in and wait for the number to stabilize.

I think I paid <$200 for the analyzer and the hose connector.