New Nitrox Diver question: Must I purchase a Gas Analyzer?

I dove about 30 dives over 3 weeks in Bonaire, and I found that I was getting pretty tired by the end of the day. Asleep by 9p kind of tired. I'd take a day off diving, and I'd be just fine again. I always dove well within my NDL, and never had any worrysome pain. Just sleepy.

So, I'm about to do another week of 2-4 dive days, and I currently taking the online PADI Nitrox course. I'm not a big fan of the online training, but, there it is.

I know from reading the board and the course material that I am responsible for making sure the mix shown on the tank is actually in the tank, and I'm pretty clear on why, (1.6 and NDL).

Yet, when I was down in Bonaire, I see the dive shop stack Nitrox tanks outside, with a piece of masking tape on them indicating the mix. The mixes shown varied from 30 to 33%, which told me the tank was probably filled by the partial pressure technique, but that is just a guess.

So, I see people just picking up these tanks, not testing anything, and just driving off. Okay, maybe they tested them later, just before the dive... (I doubt it.):shocked2:

Here is the thing. Do I need to buy a $200+ Gas Analyzer to have in my dive bag, and test all the tanks I pickup, or on the dive boat? Does a shop that does Nitrox fills, offer a analyzer for the public to use?

I'd like to know, who out there owns their own? If you don't own your own, what do you do?

Thanks everyone,

Mortis.

Must you? No. Most shops have an analyzer that you can use. The benefits of owning your own analyzer are worth considering though. For instance: You know how it works, can calibrate it, know when the sensor was changed, etc. If you're going to use the shops' analyzer just make sure you ask them to show you how to use it properly and make sure that you clearly mark your tank with the mix and MOD (especially important if you have more than one mix since you're not going to have the shops' analyzer once you're at the beach or on the boat).

I'd be leery of a shop that did nitrox fills and didn't require people to sign out their tanks... even if its banked (though that may be conservative) but definitely if it's a PP fill.

We are IANTD Nitrox Certified and do not have our own analyzers ... yet. So far where we dive, we trust the analysis of the shop (which we insist on seeing). If we were to head to unfamiliar shops down south, we definitely would bring our own.

Outside the US - you may want to bring your own or one you borrow from a buddy here in the states. IIRC, the shop can also use a blend stick to get different percentages, so assuming a partial pressure fill may be incorrect.

Depends how much you trust the dive shop and how much your life is worth to you.

I wouldn't dive those tanks without analyzing them first.

Analyzers do not need to cost $200:

EL Cheapo II Analyzer Kit : OxyCheq - DiveOps, Analyzers and Scuba Diving Equipment

I just wanted to comment on two things.

I would have been happier with your post if you had said 1.4 and MOD instead of 1.6 & NDL, but as long as you know the implications, I am fine with it.

The decision when to carry an analyzer for me is how close to the limits I am planning on diving. If am planning a dive greater than 100', I am going to make sure that the mix isn't above 33% (that gives a 1% safety margin) I will check one last time before the dive. If I am planning on a 50 minute 60' multi-level dive with 32% & it checks close at the store that has a cascade or continuous flow of nitrox, then I will be satisfied with that single analysis. One last point, this is with shops I know; other areas--not so much.

I bought one and use it regularly, though it is true most shops who vend nitrox have one. As to those who grab a tank and "believe" the sticker, that is not right. ALWAYS check your mix before using the tank so that you a) know what it is, and b) can set your computer properly. In Bonaire at Buddy Divers they require this, and have you write it on a chart before you leave with the tank. Lastly, let me say that I think you will find that the use of nitrox will definitely reduce fatigue levels. Enjoy your week of diving!
DivemasterDennis scubasnobs.com

I dive sparingly with nitrox. I watch the shop calibrate the analyzer and then watch them analyze the gas. I suppose their analyzer could be off, but so could one I buy, even if I just compared it yesterday to someone else's. All kinds of things could be off--like your analog SPG or depth gauge, even though you had the reg/console serviced last month. Diving conservatively is a hedge against this. If like 50% of my dives were nitrox I'd buy an analyzer--risk assesment.

Mortis65:

So, I see people just picking up these tanks, not testing anything, and just driving off. Okay, maybe they tested them later, just before the dive... (I doubt it.):shocked2:

Mortis.

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Mortis, did YOU look at the tanks? When my husband and I dove from the hotel, we would select tanks, analyze them on the shops analyzer, put our names, and then the shop would deliver them the next morning to the beach. We just grabbed the tanks with our names on it.

Or, I carry my own analyzer -- about 1 in 3 do. (That is a SWAG, it just seems like when the question, "Does someone have an analyzer?" is asked, about 1 in 3 offer up theirs.)

Mortis65:

I dove about 30 dives over 3 weeks in Bonaire, and I found that I was getting pretty tired by the end of the day. Asleep by 9p kind of tired. I'd take a day off diving, and I'd be just fine again. I always dove well within my NDL, and never had any worrysome pain. Just sleepy.

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These symptoms would be consistent with subclinical DCS. 30 dives over 3 weeks really isn't a ton of diving for a Bonaire trip. I would recommend slowing your ascent rate, particularly as you get closer to the surface. If you are doing deep dives, you might also want to consider incorporating deep stops in your ascent plan.

Mortis65:

Yet, when I was down in Bonaire, I see the dive shop stack Nitrox tanks outside, with a piece of masking tape on them indicating the mix. The mixes shown varied from 30 to 33%, which told me the tank was probably filled by the partial pressure technique, but that is just a guess.

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Just because the analyzed mix is varying between 30% and 33% doesn't necessarily imply partial pressure filling.
It's possible that the membrane system is pumping out slightly variable nitrox fills from day to day.
It's also possible that the O2 sensor on the analyzer may show variance in calibration, particularly when exposed over time to the elements (ambient temp/humidity on Bonaire).
If you're concerned about the fill method, ask the shop. I'm sure an employee would be happy to discuss how the nitrox is being generated.

Mortis65:

So, I see people just picking up these tanks, not testing anything, and just driving off. Okay, maybe they tested them later, just before the dive... (I doubt it.):shocked2:

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Any reputable dive shop on Bonaire or anywhere else in the world will insist that customers analyze their own nitrox.
The last time I was on the island our group purchased unlimited shore diving packages (including nitrox fills) with Dive Friends Bonaire. We analyzed every tank with the shop's O2 analyzer before using it, despite the inconvenience of analyzing 10-12 tanks at a time. That's just the way we roll. It's a safety issue.

Mortis65:

Here is the thing. Do I need to buy a $200+ Gas Analyzer to have in my dive bag, and test all the tanks I pickup, or on the dive boat? Does a shop that does Nitrox fills, offer a analyzer for the public to use?

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No, you don't have to purchase your own O2 analyzer.
Yes, I would recommend analyzing every tank of nitrox prior to use.
In my experience, every shop that offers nitrox fills will allow customers to use a shop-owned analyzer to verify the mix at the time of tank pick-up.
FWIW, I don't own my own O2 analyzer.

Something else to consider...
There are certainly circumstances where it makes sense to check the mix of an "air only" fill.
A few years ago, one of my dive buddies went to pick up several tanks at a local shop that catered to a tech diving crowd. The shop sold trimix, nitrox, argon, 100% O2, and air-only tank fills. My buddy had requested that his tanks be filled with air. For whatever reason, 2 of his "air only" fills turned out to be 100% O2! Fortunately, we are disciplined enough to always check the O2 percentage on gas fills when the dive shop has the capacity to offer higher O2 and other non-breathable gas (argon) fills.

Ask your dive shop questions about its compressor system. Ask employees whether regular maintenance and inspections are performed on-schedule. Be assertive when it comes to the ensuring the quality/composition of your breathing gas.