Nitrox Tank Marking

[Brian Gronberg]

I really appreciate the input and discussion on this topic. Being new to Nitrox I want to be sure I'm doing what I should be doing and also insuring the dive shop is not cutting corners too, whether intentional or not. I'm traveling for work right now and haven't read all of the responses but plan to tomorrow night.

 

[hroark2112]

If the air filling your tank will contaminate it, would you really want to breathe it??

There is no requirement for a permanent sticker on a tank for Nitrox. None of my tanks I use for 21%-40% have anything other than a VIP sticker and if it is >21% it has tape with the content. All other tanks have a sticker with the content (Oxygen, trimix of some sort, etc.).

 

[scubadiver888]

That's my thought too. It seems that just putting a piece of blue painters tape on them isn't the best solution.

It is what everyone in my area does. Shops have a roll of painters tape (about 2" wide), a Sharpie, pressure gauge and gas analyzer at the fill station. When your tank is filled, you are expected to test the pressure and gas in the tank. You are required to put the percentage, mod and pressure on the painters tape. Stick the tape on the shoulder of the tank so it blocks the hydro stamp.

Shops also require you to show your Nitrox card (unless the shop knows you and saw your card previously), write your name, tank serial #, percentage, mod, date and signature.

I, personally, peel the tape off my tank after I use it. When I'm removing my regulator from the valve, I pull the tape off the tank. No tape on the tank means it is used or at least it needs to be analyzed again.

 

[scubadiver888]

If the air filling your tank will contaminate it, would you really want to breathe it??

There is no requirement for a permanent sticker on a tank for Nitrox. None of my tanks I use for 21%-40% have anything other than a VIP sticker and if it is >21% it has tape with the content. All other tanks have a sticker with the content (Oxygen, trimix of some sort, etc.).

You are breathing contaminated air right now. The amount of contaminates in the air to affect your breathing is a lot higher than the amount of contaminates on a tank valve to cause a fire. I never really paid close attention when chatting with guys who serviced the compressors. I vaguely remember something like air needs to be filtered something like 5 times to be acceptable for breathing underwater at recreational levels. But if the tank is going to be exposed to greater than 40% oxygen the air should be filtered 7 times. Something like that.

The whole thing is also not true or false. If I have an O2 clean tank and I fill it once from a source which is filtered enough for breathing but not enough for exposure to 100% oxygen there probably won't be enough contaminate to be an issue. If I fill that tank 1,000 then fill it with 100% oxygen it will probably cause a fire. Now will a fire happen at 500 fills? 250 fills? Hard to saw. Additionally, with enough pressure air will cause a fire. So if the filler is filling the tank faster than 600 psig/minute, the faster they are filling it, the higher the chance a fire will occur.

In other words, it isn't predictable as to when a fire will occur. Just like DCS, if you follow all the rules you SHOULDN'T get bent. But even when following all the rules, people get bent. The less you follow the rules the greater chance, statistically, you have of things going wrong.

 

[tbone1004]

@scubadiver888 yeah there is no 5-7x filter steps. Max I have ever seen is 3 but even that is only on big fill stations

 

[scubadiver888]

@scubadiver888 yeah there is no 5-7x filter steps. Max I have ever seen is 3 but even that is only on big fill stations

Yeah, like I said, I wasn't really paying close attention to the details. I learn by reading. If you tell me something and I don't write it down I'll forget most of it. Hmm, thinking back to the first compressor I saw, there were two large cylinders. I'm guessing those were the filters. Now you got me wondering how compressors work. I'll have to read up on it.

 

[J-Vo]

I've seen Nitrox bands on more air filled rental tanks then I have on Nitrox rental tanks. The only marking that means anything is the analysis sticker that I created myself.

 

[tbone1004]

Yeah, like I said, I wasn't really paying close attention to the details. I learn by reading. If you tell me something and I don't write it down I'll forget most of it. Hmm, thinking back to the first compressor I saw, there were two large cylinders. I'm guessing those were the filters. Now you got me wondering how compressors work. I'll have to read up on it.

read your heart out.
The first big filter was likely the water filter that takes most all of the nasty's out and is literally just a big open tube. The last one contains the actual filter cartridge where things like CO are converted to CO2 if equipped, and everything else is taken out. Sometimes there will be a second filter stack, but again that is usually reserved for BIG air compressors to keep the size of the filter stacks reasonable.
Filter System Design

 

[In2theabyss]

I thought the same. Does everyone reanalyze to confirm the blend percentage on rentals?

Every time......

 

[boulderjohn]

I thought the same. Does everyone reanalyze to confirm the blend percentage on rentals?

Every time......

I have seen posts like this over the years on ScubaBoard, posts that suggest that the writer believes no one actually analyzes their tanks. I keep wondering where these people are diving. I don't believe I have ever experienced a situation where I have rented nitrox tanks and not been expected to analyze the blend on the premises, and I have gotten nitrox in a lot of places over a lot of years.