Used Alum 80s filled with Nitrox

[captain]

Do you know what mix is in them? It's very easy to find out the MOD (maximum depth you can dive with that mix) once you know the O2 percentage. If I were in your position, I'd find that out and just dive with them, AS LONG AS you don't go anywhere near the MOD, and AS LONG AS the mix is under 40%. No reason to waste a good $20 worth of nitrox. Do you have a computer? If so, and you know the mix, you can set your computer to that mix and dive away, or if not, just dive on air tables. If you are well short of the MOD and calculate N2 loading just like normal on air, you'll be fine. Once you've used up this fill, then remove the sticker and fill with air.

There are only a few really serious safety considerations with using these tanks as is. One, don't exceed the MOD( for the third time), and make sure you know what the MOD is at 1.4pp for that blend. (There are lots of places to find out that info) Two, there is a maximum allowable O2 exposure for a given 24 hr period, but if you only have 2 dives' worth, you won't go anywhere near that. Three, you must really know what the mix is, and that means having someone analyze them. If you have a buddy that's nitrox certified and can dive with him/her, all the better. Truthfully there is no great mystery or skill associated with using nitrox, the main things are to know what the blend is (with confidence) and do not dive too deep for that blend. It's really that simple in this case. (2 tanks already filled and analyzed) Extended nitrox use, planning dives for a particular blend (or blend for a particular dive), dealing with accumulated O2 exposure, etc, those are the sorts of things covered in the course.

I can already hear the flamethrowers warming up, so I would also advise you to: 1) take this as a sign and just take a nitrox course, then use the tanks, and 2) If you are not comfortable in any way with using them while not nitrox certified, don't.

You are giving away closely guarded secrets. You will be hunted down.

 

[Florabama]

I purchased two used Alum 80s - hydros good till 2013. Unfortunately they are filled with Nitrox (newbie here, so I can't use). is there anything special that needs to be done berfore filling them with air, short of emptying them?

Take a nitrox course and dive them. Don't know about your area, but at our shop, it's only $99 bucks and takes one evening. While I'm not a C-card nasi, the only problem with learning on your own is that most shops still wouldn't give you fills without a card even if you demonstrate understanding of the theory, so you would probably have to fill them yourself. If that's at all interesting to you, order Vance Harlow's Oxygen Hacker's Companion. In fact, order it anyway and study it even if you decide to get the card and fill conventionally. By doing so, you'll have a far deeper understanding than most people --even instructors -- of the issues with nitrox.

In my opinion, nitrox and nitrox dive computers are the two greatest innovations to come along in recreational diving in 40 years.

 

[halocline]

Matt,

While I agree diving nitrox isn't rocket science, you're a DM advocating "learning to dive nitrox on the internet" :shocked2:

I knew I'd get kind of flamed for this, but I'm not advocating "learning to dive nitrox on the internet", I actually did advise him to take a nitrox course. What I did say, was that if he knew the blend and MOD, and if he was comfortable staying well above the MOD, there was no reason to drain the tanks rather than use them.

Here's a perfect example. Let's assume for the moment that this is a 32% mix, the most common banked nitrox. That puts the 1.4ppO2 MOD at 111 ft. Now, assume that he's on a lake, river, or quarry dive with a maximum depth of around 50-60 ft, pretty typical for many local dives. He also only has two small (AL80) tanks of the stuff. Personally, I can't see any additional danger diving with these tanks in this situation rather than draining the tanks and filling them with air. Do you?

It does break the rules, so I guess I am a bad DM.

 

[Rick Inman]

I enjoy breaking a few "rules" myself.

Personally, I think that diving nitrox is so easy it should be taught in BOW.

But I also stand firm that any gas dived should be analyzed by the diver who is breathing it. Know thy mix. So, if you know the mix, and you know the MOD, that's it. Go dive the things. A couple of single AL80's - you're not going to need to worry about OTUs and max exposure times.

 

[ktgould]

I enjoy breaking a few "rules" myself.

Personally, I think that diving nitrox is so easy it should be taught in BOW.

But I also stand firm that any gas dived should be analyzed by the diver who is breathing it. Know thy mix. So, if you know the mix, and you know the MOD, that's it. Go dive the things. A couple of single AL80's - you're not going to need to worry about OTUs and max exposure times.

I'm planning a trip this summer and was going to try to be nitrox certified for that anyway. I wasn't taking tanks with me, but I thought it a good idea as I see a lot of boats dive nitrox as a rule. I just wanted to be certain I didn't need to "scrub" the tank I'm keeping for air.

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