Is a Nitrox test at the dive site necessary?

[XS-NRG]

Do as you want but unless you can 100% guarantee the exact tank YOU analyzed and didn't let it out of your site (including when transporting with other peoples) you will want to check right before the dive. I like the comment above about your buddy knowing what mix you are running should they have to breathe off your tank. If you were going to omit one of the two analyzing sessions it would be the one at the shop you got the fill. That way you are still checking right before or at your dive and know exactly what's up. Obviously being a bit facetious there but you get my point.

 

[Shipwreckscanada]

Follow up,


I just received the March/April edition of Dive Training magazine. On page 90 author Cathryn Castle says and I quote…


“Before even setting up your gear on a tank containing nitrox, the first thing you must so is verify its contents. This is done with a device called an oxygen analyzer.”


“By getting nitrox-certified and diligently verifying your nitrox tanks contents before each dive, you can increase your diving safety.”

 

[Steve_C]

I verify when tanks are filled and labeled.
Tanks are in my possession until the dive.
Tanks have unique markings.
I am 100% sure that I am diving my own tank.
I do not measure again on site.

 

[Storker]

You mean just like Carlos Fonseca was 100% sure?

 

[jhnmdahl]

Fonseca didn't mark the bottle with the fill, or initial/sign a label indicating the fill. Quite the opposite - he used a bottle marked only "oxygen" believing it contained something other than only oxygen.

This thread hints at, but does not directly discuss, best practices that can be tested against accidents such as these to ensure that the best practices will prevent such deaths. If I analyze a tank at the scuba shop, and affix a label and sign it, I don't know of any actual scenarios in which I would have had problems not analyzing it again later.

I'm trying to imagine a scenario in which a sloppy operator could knock the label off and inadvertently re-affix it to another tank or some such thing, but this seems pretty unlikely. Nevertheless, I would feel a temptation to re-test if the tank had been out of my possession.

John

 

[eelnoraa]

When only dive 32%, I only analyse at the shop when I pickup. I own my tanks. All tank only have 32%, no chance of diving a wrong mix. When I start diving other mixes, I always check on the day of the dive. Not necessary at the site, but anytime I have a doubt, it is a 1 minutes job for peace of mind.

 

[USdiver1]

If you have a perfect memory (hint: nobody does) and can be 100% positive about the chain of custody concerning your filled cylinders, then maybe a single analysis at the fill station with proper marking and initials can work. However, as we humans are not infallible and have been known to err when writing down numbers, placing the tape on the wrong cylinder, etc.; I would recommend that you check/analyze O2 content when at the dive site as well as at the fill station. As others have stated, it can be a matter of life and death.

 

[Patoux01]

placing the tape on the wrong cylinder, etc..

If you really manage to do this, then yes, please, double, triple check (or more). I'm arrogant enough to know I do not make such a mistake.

 

[Basking Ridge Diver]

[QUOTE="USdiver1, post: 7652083, member: 124708" As others have stated, it can be a matter of life and death.[/QUOTE]

The really good thing is it is only your life. So you can check or not - me I don't check on site. I am only risking myself.

 

[Steve_C]

At the LDS my tanks are separated out. I test and label. I carry to my car and take home. I transport to the dive location. On the boat I verify that I am using my tanks since crew helps carry on. My two HP100s always have a mix in the 30-32 range. My AL19 always has air.
There is nothing to remember. The only danger is if somebody breaks into my house and changes my mix in an attempt to assinate me. But then I got bigger problems.