Permanent MOD markings on tanks

[mtherr]

In an accident analysis thread, a participant made a point that permanent markings and not temporary markings should be used to identify scuba tank contents.

I believe this practice got kick started with the WKPP project and it proved to be a safe way (combined with operational procedures) to execute complex dives involving various travel, bottom and deco mixes.

Many people seem to have adopted this practice only partially. While diving at Ginnie and Peacock mostly in the last couple of years, I saw tanks with all sorts of MOD that made me believe they were not dedicated tanks. At Ginnie, in my last two trips, I noticed stages with MODs from 70 feet to 130. I rented myself a 100 foot tank that was not filled with EAN 34.

My practice when cave diving (single gas + o2) is to analyze all main, stage and deco bottles when the gear is setted up (on stages, I analyze when ready to install my regulator). On Caribbean dive trips, I analyze, mark and log analyses as per recreational standards.

Am I alone feeling that permanently marked tanks are not dedicated in real life?

[PfcAJ]

I own enough tanks to permanently mark them for all the gases I use. Al80s are cheap. I believe that if one is going to be doing dives involving multiple tanks, its worth the cost to buy and dedicate tanks for each specific gas.

I also analyze at the fill station. I don't take a tank out of the fill area that isn't analyzed, taped, and marked with the o2 content, date, and my initials.

[gianaameri]

There is only two pieces of information I need on a tank when I dive and that is my name and the MOD.

Any more than that is unnecessary and can lead to confusion whilst diving.

They are placed on the tank using a Permanent Black Wide-tip Marker after the tank is analysed.

If need be, with solvent the markings can be easily removed, and new markings placed on the tank (or refresh the old ones as needed by running the black marker on top of the existing writing).

My favourite place to mark the tanks is on the neck nearer to the valve.

Not exactly DIR, but it works (for me).

[JamesK]

I own enough tanks to permanently mark them for all the gases I use. Al80s are cheap. I believe that if one is going to be doing dives involving multiple tanks, its worth the cost to buy and dedicate tanks for each specific gas.

I also analyze at the fill station. I don't take a tank out of the fill area that isn't analyzed, taped, and marked with the o2 content, date, and my initials.

Same here.


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[TONY CHANEY]

interesting thought Gianaameri.

[skip]

My bottom mix tanks have no permanent markings regarding content. They could be anything from Nitrox to Air to Hypoxic. My stage tanks have permanent MOD markings (one on side of tank and another at neck) and are filled only with the gas for that MOD. My deco tanks are likewise permanently marked in large numerals (and the word "oxygen"). The exact percentage on all of them is marked on duct tape. Of course they all get analyzed just before diving them to verify actual contents, including CO analyzer. It's what I was taught to do by TDI and the NACD (except the CO, I added that after the brandon accident).

skip

[kwinter]

When people talk about MOD markings, I have learned that they don't necessarily mean the same thing. MOD is determined at a particular pO2. Some people mark their tanks for MOD at 1.4. Others at 1.6. I even know someone who marks his for 2.0. For this reason, my tanks do not have permanent markings. Gaffers tape and a Sharpie work fine. Most of the time I only label the mix and can do the math in my head. If I do mark MOD, they are marked "[email protected]". If I lend a tank or swap with someone, I want them to know.

Now everyone can feel free to tell me what a moron I am.

[cavediver256]

Ken, I don't think that is a moronic method at all.... At least with duct tape, you analyze the gas, write down your findings, with the date and time....A TANK MISSING DUCT TAPE???? ANALYZE IT AGAIN !!!!!! It seems to me, permanent MOD markings that you placed on a tank 2 or 3 years ago might get ya killed

[skip]

Ken, I don't think that is a moronic method at all.... At least with duct tape, you analyze the gas, write down your findings, with the date and time....A TANK MISSING DUCT TAPE???? ANALYZE IT AGAIN !!!!!! It seems to me, permanent MOD markings that you placed on a tank 2 or 3 years ago might get ya killed

permanent markings will not kill anyone, no matter how old they are. of course the whole point of permanent markings is that those tanks have appropriate mix in them at all times; the whole point of permanent marking is that the gas within is also of "permanent" mix. period. I think the current incident, thinking you put air in a tank that actually had O2, is a good indication of the trouble you can get into by NOT using permanent markings and following through. No good to mark a tank DECO or OXYGEN 20, then putting air in it and noting it on tape that comes loose in travel or water! The permanent marking is not the problem here.

I've never trusted duct tape or sharpie on tank. I only know that was the mix or MOD at some unknown past time (unless date is included and maybe psi too). so if using nonmarked tanks that may have any mix in them it's best to add date it was last analyzed, psi it had at that time, and mix as well. I don't like marking them with percentage alone (or ppo2) - I am very comfortable knowing that my permanently marked tanks will always be filled with a mix that is good to the indicated MOD (e.g, 20, 70, 100, etc.). I always analyze prior to a dive to verify the mix is indeed acceptable to the indicated MOD, but I can't really see a downside to the permanent marking other than loss of ability to use that same tank for any mix, any MOD.

Whether one uses permanent markings or not, I think we can all agree that marking the MOD, and the Percentage of O2 (and He if trimix), AND analyzing at some point close to dive time to verify contents, is essential and proper gas management. Last year, Brandon died because the contents were not analyzed for CO and taught us all to pay attention to that gas as well. Now Carlos is gone due to a failure to analyze the mix for oxygen content! Brandon followed best practices and taught us a new best practice. Now another diver failed to follow well-established gas management recommendations in terms of knowing for sure what you are breathing and marking the tank accordingly and has got us all talking about what we think is best practice in tank markings and knowing your mix. An experienced cave and technical diver made a simple mistake and paid the ultimate price. Let's hope that his death spurs us all to reconsider and reevaluate our tank analysis and marking practices and thereby saves lives.

I first thought that "complacency" as a new guideline for cave divers was a crock - seemed like it was a catch-all that was covered already by the other guidelines. Now I'm not so sure. Perhaps it does deserve it's own place in the list.

skip

[Bobby]

I have dedicated deco/stage cylinders for depths to 245'. All cylinders dedicated for below 130' have my name and MOD on the side of the cylinder and MOD with the mix on the neck permanently marked. From 130 and shallower, except oxygen, have my name and MOD permanently on the side and I use duct tape with a sharpie to put the MOD and mix on the neck as I will accept mixes that are a little off for shallower depths. All Oxygen is permanently dedicated for O2 and the cylinders are green so they can not be confused as anything other than O2.