Mistaken identity: travel and deco gas mixup

[Storker]

^^^ This.

When I took my nitrox cert, I was a bit amazed to hear that people dived mixed gas without having their own, personal analyzer. That was my first gear purchase after that cert, and my gear setup routine now involves analyzing the tank to verify its contents just before I mount the 1st stage on the tank. Every time.

 

[Neilwood]

Not being Nitrox certified, I could be speaking out of a hole in my head but my thoughts would be for a lot of tanks it would be worthwhile devising a system:
1) Tanks are filled, checked and marked by 1 person
2) These tanks are rechecked by another person independently from the first person. Any deviation leads to the tank being rechecked by both.
3) There is a clear method of identifying each tank and its status (possibly with a wrap of differently coloured electrical tape designating its status ie blue for 32%, red for 50%) and have it applied to the valve stem. This being independent of the normal marking.

That way everyone knows that each tank has been checked and rechecked and they can immediately see what it is without having to check.

 

[bl6394]

Not being Nitrox certified, I could be speaking out of a hole in my head but my thoughts would be for a lot of tanks it would be worthwhile devising a system:
1) Tanks are filled, checked and marked by 1 person
2) These tanks are rechecked by another person independently from the first person. Any deviation leads to the tank being rechecked by both.
3) There is a clear method of identifying each tank and its status (possibly with a wrap of differently coloured electrical tape designating its status ie blue for 32%, red for 50%) and have it applied to the valve stem. This being independent of the normal marking.

That way everyone knows that each tank has been checked and rechecked and they can immediately see what it is without having to check.

Why would I unnecessarily place my life in someone else's hands?

Even if we had Person A to initially mark the tanks, and another Person B to verify - if I am not both those people - I would always personally analyze the tanks and mark them myself. If either Person A and / or Person B made a mistake - then I would bear the consequences. And if I'm already personally analyzing and labeling - why bother with Person A and / or Person B. Remember, personally calibrating an analyzer, analyzing, and labeling your gasses are required skills for Nitrox through Adv Trimix classes. If you aren't comfortable with the skills or you don't have access to the equipment - you shouldn't be doing those dives.

It's what I teach in my Enriched Air class: personally analyze and label your own cylinders. Confirm your gas' as you breath on your dive. If you make a mistake - only you bear the consequences.

 

[Storker]

I usually fill myself, as my club has a nitrox mixing system, so my procedure is:

1. Fill tanks, monitoring that the mixer shows the correct mix
2. Analyze tank with external analyzer, immediately mark tank with mix, MOD, date and initials. I use a black felt tip pen and ordinary painter's tape on the shoulder of the tank.
3. If filling 300 bar tanks: wait until the tank has cooled off, top up with EAN21 (AKA air), leave for mixing/diffusion, re-analyze, then immediately mark the tank with mix, MOD, date, initials and pressure.
4. Wrap one turn of yellow-and-green electrical tape around the valve opening to indicate nitrox (if I fill air, I use ordinary painter's tape). I don't see any point in more different color-codings than air or nitrox since I don't do staged accelerated deco and is only certified up to 40%.
5. On the site, I use my personal analyzer to verify the tank contents. If the mix is less than 1% unit off what I've marked on the tank, I attach the reg.

If I get my fill at an LDS, I of course drop step 1.
If I top up a tank with another mix than was in it (including air), I do a quick calculation before filling about what mix to expect. I have a small Excel sheet I've made for that purpose, and I've got it on my Android phone.

This procedure may seem slightly paranoid, but the two analyses with different analyzers secures against faulty analyzers, errors made during marking the tanks and other, less probable problems. And I won't dive a tank that I haven't analyzed personally at least once.

 

[DA Aquamaster]

I wasn't aware of the need to re-invent the wheel. Standards and protocols have been in place a long time.

If it is a single tank, single gas dive:

1. the gas should be analyzed by the gas blender when tank is filled,
2. the tank should be immediately labeled with the pressure, percentage of O2 (and He if applicable), and the MOD of the mix. That label needs to be stuck to the tank, not just hung on the valve; and as the OP suggests, it should be immediately labeled before he or she moves on to the next tank;
3. the diver should analyze and verify the mix just prior to the dive, providing an additional verification that the gas matches the contents label and that it is appropriate for the planned dive.

If the dive will involve multiple gasses, in addition to 1-3;

4. the tank should be marked with the MOD in large numbers so that teammates can also verify you are switching to the correct gas.
5. That large MOD label also means that someone filling the tank needs to refuse to fill that tank with a gas that does not comply with that MOD label. If that tank is going to have a different gas, the MOD label needs to be removed and replaced with an appropriate MOD label.