POLL, Nitrox tank use and analyze

[Mossman]

This is interesting to me ... because a shop or boat has provided me with an analyzer to check every tank I've ever used.

Has my experience been uncommon?

Not uncommon, but it's a dangerous assumption that ALL boats will provide you with an analyzer or that ALL shops will let you analyze the tanks. See my previous post for examples of each. I was pretty surprised on my last trip when the boat didn't have an analyzer aboard because that was a first for me - it's rare, but it can happen. Next time, I'll be sure to ask in advance just in case.

 

[lowviz]

.....//.....I know that GUE is one of the few (only?) agencies that doesn't require it. All the mainstream recreational agencies do. GUE is a tiny percentage of the market - and their divers have particular training and use mixed gasses as standard. Their rules simply don't apply to the average OW recreational diver. I still think their outlook is irresponsible - because GUE divers do share boats with non-GUE divers... and should be aware that accidents can happen when kit gets muddled, picked up by the wrong people...and those divers might not understand GUE protocols........//......

First, I'm not GUE trained and certainly not one of their biggest defenders, but I do respect that they seem to be highly disciplined and self-consistent.

Shamelessly copied from GUE (Web):

Cylinder Marking: The Fine Points
Cylinders should be stripped of all unnecessary stickers (place VIP on bottom), Nitrox banners or other non-essential markings. Numerous markings create dangerous confusion. Each cylinder should be marked horizontally on two sides with large three-inch high numbers identifying its MOD (Maximum Operating Depth). Oxygen cylinders should be marked "20" with the word OXYGEN written horizontally along the tank, preventing divers from mistaking "20" with "70" or "120".
The diver's name should also be marked on the cylinders to simplify identification. Last name should be used to avoid confusion. No gas percentages should be placed on the cylinder for identification purposes, as these require divers to make underwater calculations. Any content information is the result of analysis and should be placed near the neck of the bottle. For example, when analyzed, a 18.2% oxygen and 45% helium mixture would read 18.2/45; when analyzed, a 32% Nitrox mixture would read 32.0%. The date analyzed and tester's initials should be included with the percentage marking.

You alluded to it, but I'll go so far as to say it: IMHO GUE gets a "pass" on tank marking. They do mark tanks (cylinders) but they do it their own way -go figure.

Anyone that would confuse a GUE cylinder marked with a last name, "20", and "OXYGEN" for their own air cylinder really doesn't comprehend the most basic hazards of diving. The bigger issue (from my perspective) is that this brings into question that standards may have been lowered too far. Do we really need to protect OW / AOW divers from this threat? Aren't divers still being trained to be not just sure, but damned sure, of what they are planning to breathe?

 

[Akimbo]

Interesting question. Most of the mixed gas I have used commercially required having faith in others (enough to stake my life on) to properly analyze before sending it down the hose. Some of this mindset carried into recreational Nitrox. There are some individuals I trust to correctly analyze the gas, some fills I will witness the shop calibrate to air and analyze, and others I put my meter on.

Technically, most of the millions of cubic feet of HeO2 I/we sent to divers ultimately depended on faith in people we didn’t know. Most mixes used in Sat were between 1 and 4% Oxygen, which is too low to reliably calibrate an analyzer to with air. We ordered laboratory grade calibration gas mixtures to cal our instruments. The only real cross check we had with available instruments (essentially the same instruments Nitrox divers use) was to stick a sensor in a mask and read the PPO2 at depth. Even then, internal analyzers were calibrated using the same cal gas sent from shore. We did cross check newly received cylinders of cal gas to other bottles that were already in use so there was some reassurance there.

A side note: The cal gasses were mixed by weight on precision scales to +/-0.05% accuracy. No other instrument was used by the gas supplier to verify, at least through the 1980s. I don’t know if they use a mass spec or gas chromatograph now or not.

 

[lowviz]

..//... There are some individuals I trust to correctly analyze the gas, some fills I will witness the shop calibrate to air and analyze, and others I put my meter on....//....

With any of the above, that is your way of being damned sure. Wish every new diver thought that way...

 

[lowviz]

....//....Most mixes used in Sat were between 1 and 4% Oxygen, which is too low to reliably calibrate an analyzer to with air. ....//.....

Zeroed on air, my oxygen analyzer reads between 0.1 and 0.5 when breathing welding argon. -I would have to agree with your observation.

 

[Akimbo]

With any of the above, that is your way of being damned sure. Wish every new diver thought that way...

Carrying the concept of trust another step, how often do we check the air sample reports on the dive shop or charter boat’s compressor? I am less concerned over the oxygen level in Nitrox than the Carbon Monoxide and hydrocarbon levels, Nitrox or air. That was something we only worried about on air dives offshore (LP air compressors, often Diesel powered) since mixed gasses were all cryogenically purified. I have seen compressor air intakes at dive shops way too close to parking spaces. Sure enough, people would back in close to the compressor, let their engine run, and pick up/drop off bottles.

Look at the faith many people put in their LDS to service their regulators… using the same bench they repair outboards on. Interesting and thought-provoking topic… but it is making me worry about the breaks on my van.

 

[lowviz]

Carrying the concept of trust another step, how often do we check the air sample reports on the dive shop or charter boat’s compressor? I am less concerned over the oxygen level in Nitrox than the Carbon Monoxide and hydrocarbon levels, Nitrox or air. That was something we only worried about on air dives offshore (LP air compressors, often Diesel powered) since mixed gasses were all cryogenically purified. I have seen compressor air intakes at dive shops way too close to parking spaces. Sure enough, people would back in close to the compressor, let their engine run, and pick up/drop off bottles.

Look at the faith many people put in their LDS to service their regulators… using the same bench they repair outboards on. Interesting and thought-provoking topic… but it is making me worry about the breaks on my van.

Being a local diver with a lot of cylinders, I can use my LDS for just about all of my fills. The little things are what help to build trust, like where their compressor intake is and the time I forgot to specify the IP for my coldwater regs. They came back spot-on for where I want them. The store later said that they record anything special that a customer asks for and tend to use that when in doubt.


As for CO on vacation, you and Dandy Don pushed me over the edge. I'll buy the CO anlayzer.

 

[ajduplessis]

Always know what you breath!

 

[D_B]

I know that PADI says that a yellow / green band is "required" in the nitrox manual, but if you do a search on required Nitrox tank markings you will find other info.

I've been on a live aboard trip and also local boat diving, no sticker is required more than a MOD sticker and to show your cert card for nitrox when asking for nitrox (banked nitrox, no partial pressure blending)

I agree that a tank should be marked with it's contents, and maybe even a yellow/green sticker would be OK, but it does not have to a billboard to accomplish that
... I should think common sense would have anyone picking up a tank to dive should very well make sure that it's "their" tank

 

[Adobo]

Pretty much my approach. Cylinders are always analyzed both at pick up (why leave the shop if the gas is wrong?) and then the day of the dive (to make absolute sure it's the correct mix before using it). I'd be willing to trust my wife's analysis of our cylinders. That's about it.

To me, these seem like two fundamentally different approaches. Your approach checks to make sure that the tanks you are bringing to go diving that day have the mix that you expect them to have.

Whereas the other approach checks to make sure that at the dive shop, the tanks have the right mix.

In my case, I usually use two al80s in addition to my backgas. One al80 is used for 100ft and shallower. The other is used for 70ft and shallower. If I were to bring both of these tanks to the dive shop to be refilled after a day's worth of diving, it is conceivable that when i pick them up, I get the proper readings on the analyzer but then inadvertently put the analysis tape on the wrong tanks (put the 100ft analysis on the 70ft bottle and vice versa).

Now, in your approach, you should be able to pick up this mistake when either you or your wife does the analysis on the tanks on the day of the dive. In the other example, I am not sure what happens.

Also, I am not clear on what some agencies teach in terms of labeling stage/deco bottles. Maybe the labeling system is meant to catch this type of mistake also. Or maybe not.