Air Refills Mixing With NITROX Gas Remains...

[Joe-Diver]

But it wasn't a regular air fill. It was an air top off on a tank full of Nitrox, and you know it. Why would you not analyze the gas when you picked up the cylinders? This is not a shop problem. This is a diver problem. It is always our own responsibility to know what is in the cylinders we are breathing.

BINGO....Big X2 on that post.

 

[Flightlead]

Maybe you should always check your mix if you are diving with tanks used for nitrox?

I vote for this being the correct answer

 

[Ironman]

The issue: If I follow my usual routine and just drop the tanks off for an air fill, the shop will not know I used those tanks for NITROX.

Well, if you used the tanks for nitrox, there should be a decal or sticker affixed to the tank, indicating the contents. If nitrox was put in, and no sticker was put on, that is inappropriate, and a safety concern. And, while it is tempting to take these off after a dive (after all, WE know what was in them, and WE know that the tank has been used, even if others might not), it is helpful to the person doing to next fill to have them left on. In addition, if a tank is used for enriched air, you ideally should have a decal / band around the tank shoulder indicating that, not so much for you as for others, including personnel filling the tanks. Some folks whine about having these on tanks. Let ‘em. It is much easier for a shop to see a 6" nitrox wrap, which may prompt them to ask you what was in the tank before hand, than to see the smaller contents labels that are frequently used for the specific mix. Several agencies even state this as part of their enriched air training.

I have never had a shop ask me what % mix was in the tank, nor have I seen them test it beforehand. They just fill it; creating a situation where I could end up diving past the recommended mix depth inadvertently.

Two points: 1) As several experienced SB folks have mentioned, it is up to you to know what is in your tank. If you have enriched air in the tank, and your residual pressure is something greater than 0 PSI, and you put air in the tank, you will have a resulting mix that is slightly 'richer' than air. How much will depend on the nitrox mix, ending pressure, etc. But, you should know what was in the tank when you brought it in, and analyze it after the fill to know what is in it afterward. 2) If there is a nitrox decal on a tank, a shop should ALWAYS ask, 'What is/was in the tank? Do you want the final mixture to be no more than 21%, or whatever blend we will have after filling with air?' If you take a tank with a nitrox decal in for an air fill, and no one says anything to you about what might be in the tank (and whether or not you want a 21% mix after filling), you really need to question the operation's procedures. Now, if there is no decal on the tank indicating that the tank is used for enriched air, and there is no sticker indicating the tank contents, and the customer requests an air fill, chances are a shop won't test the tank contents (see exception, below). In a high volume operation it is simply not cost-efficient. (And, if you think shops should analyze the contents of EVERY tank brought in for an air fill, then be prepared to pay the extra cost.) If I have 20 tanks lined up for air fills, I put the ones with a nitrox decal aside, and fill the other tanks first. Then, I go through the decal tanks, and frequently check the contents, even if there is a contents sticker on the tank. Every tank that comes in for a nitrox fill has to has a band. Every tank with a band, has to have a nitrox fill slip filled out, even if the customer only wants air. That way, we have a double check on the contents sticker, AND we know what final mixture they want.

Does your local shop have procedures in place to stop this from happening?

In several ways. First, we don't put nitrox in tanks that don't have big green and yellow nitrox wrap. As noted, that practices irritates some (a very few), but it is a reasonable and conservative practice. Second, we require a fill slip for all nitrox-labelled tanks. Third, we inspect the VIP sticker (we really do) for each tank, before each fill of any kind (as well as the hydro date). The VIP sticker may not tell us about content, but an 'Oxygen Clean' VIP sticker will cause us to analyze the residual mixture, even in the absence of other, usually appropriate labeling. Fourth, in examining the VIP, we generally look for any other stickers on the tank, specifically including a nitrox contents sticker. Is this perfect? No. But, it generally gets the job done, and having such a policy demonstrates due diligence.

 

[RJP]

Due to it being a regular air fill, I would not think to analyze the tank when I got it back.

That's what's known as "user error" in my book. I would never dive any tank - nitrox marked or not - that I didn't personally analyze.

 

[Thalassamania]

Youre responsible for analyzing your tank.

Actually that's a half truth. The person filling the tank is responsible for analyzing the tank and logging the fill and you are also responsible for analyzing the tank and signing the log.

 

[reeldreams]

doesn't everyone analize there own tanks if not you should even after you top the tanks with air

 

[String]

Actually that's a half truth. The person filling the tank is responsible for analyzing the tank and logging the fill and you are also responsible for analyzing the tank and signing the log.

Depends on country.

 

[Thalassamania]

That's not done in the UK? Or rather, I should ask, where is that not done?

 

[1_T_Submariner]

I nwould analyze any tank with a nitrox sticker on it. It's not hard. I have analyzed tanks that came off the same filling manafold (they where the same but I checked both anyway).

 

[String]

That's not done in the UK? Or rather, I should ask, where is that not done?

Although some shops make you sign a fill log its not a legal requirement.

The responsibility is solely on the person requesting and buying the gas for verifying its contents and use. (You dont need cards to buy gas either by law although some places annoyingly ask for them).

I personally like it that way - responsibility should always lie with the end user.

Can think of a few other european countries the same.