Question NITROX (in less than 40 foot of water)

[BlueTrin]

Like others said, don’t dive with mystery gas … if you can certify its composition, just don’t dive it …

 

[rjack321]

I know the person I asked dives in Cozumel and every shop can get air or nitrox tanks. But the point remains, every day thousands of "air" divers use tanks provided by dive charters or filled by shops that can do both. Should they be analyzing?

As a general rule, yes. Tanks get mixed up all the time.

 

[rjack321]

That's more than enough to support my position. I was responding to several statements that it's dangerous to not know exactly what is in your tank by showing that many divers do not know. Furthermore, they are not taught to know. No agency is telling "air" divers to analyze their tanks in case they somehow got filled with something other than air. Apparently, it's good enough to trust the dive shops when they say "here, this is an air tank". Then they take a EAN course and are taught to analyze tanks and suddenly the same dive shop cannot be trusted when they say "here, this is a 32% EAN tank".

News flash!!!
The dive industry isn't consistent and is even contradictory.

Nowadays don't dive any gas unless you know who filled it (and the general state of their compressor maintenance) and what is in the tank. O2 and CO being the most critical analytes.

 

[L13]

As a general rule, yes. Tanks get mixed up all the time.

Are you sure? I don't remember the last time an incident occurred where an air diver got nitrox. Do you?

However, this just lends strength to my argument that all modern OW scuba classes should include Nitrox certification. If you can't dive air without verifying the contents your self, they you can't dive till Nitrox Certified.

 

[ReefHound]

Are you sure? I don't remember the last time an incident occurred where an air diver got nitrox. Do you?

However, this just lends strength to my argument that all modern OW scuba classes should include Nitrox certification. If you can't dive air without verifying the contents your self, they you can't dive till Nitrox Certified.

I don't know of any recent incidents but I don't think that indicates that air tanks aren't getting filled with nitrox, I think it indicates that the vast majority of dive profiles can handle the mixup without consequences. The MOD for 32% is 111' at 1.4 (deeper for 1.6 and you don't go into convulsions the instant you exceed) while the max depth for recreational divers is 130' so there is a narrow band there. The air diver will not be spending much time at those depths, either.

 

[myrddin]

I wanted to follow up and mention that I did get the tanks analyzed. They show exactly what the % is on the sticker. So now I can state that I saw it with my own eyes. There fine. Next question. Once these tanks are empty. Or low. Can they be filled with air?

 

[MaxBottomtime]

Absolutely. I have been diving nitrox almost exclusively for a number of years, but I decided to use up an old airfill card I had lying around. I've got about twenty air dives before putting nitrox back in my tanks.

 

[Russjstewart]

I once analysed a hire tank and shut the valve when I got to 60%. The charter was partial pressure blending and I am betting they had added air, I did not put a gauge on it it see pressue. Whenever I have brought used tanks I always dump the air and get a fill from a known source

 

[jborg]

Are you sure? I don't remember the last time an incident occurred where an air diver got nitrox. Do you?

Last time I was in Egypt, yes. After a dive, one of the DMs pointed out the nitrox sticker on one of the customer's tanks and asked if they had intended to dive that since they weren't on the sheet as one of the nitrox divers. The expected "no, what's that, what does it mean" discussion ensued. They didn't know nitrox was a thing and had just grabbed one of the tanks and checked the pressure when switching between dives. (It wasn't always obvious which tanks were which; there were stickers, but they were old, worn, and sometimes reduced to just a few pieces of greenish tape. No other labelling as divers were expected to analyze them themselves.)

I think they were a fairly new OW diver, so at least somewhat unlikely to run into trouble with any 21-32% gas, given their dive profile.

 

[rjgiddings]

I'll second ( or third, or fourth?) the opinion that taking a Nitrox class will help you understand PPO2, equivalent air depths, MOD, oxygen toxicity etc., and all the terms that Nitrox training will introduce. And really if you ever huff off a Nitrox cylinder you should know this stuff. It's not voodoo.

I can never recommend breathing a gas that you're not already trained/ certified to use though.

There's a few instructors here in Seattle that will tell you a diver NOT analyzing / marking their cylinders is a hot button issue for them !