How do you mark your stages?

[Doc Harry]

I can't make up my mind how I am going to mark my stage bottle.

I have a 14-cubic foot stage bottle for soloing. I fill it with air.

Since pO2=1.4 at 190 feet for air, should I mark it 190 even though I'd never go that deep on air?

What do you do?

 

[Jim Lapenta]

Harry, any bottle I use for air gets marked with date, mix, and my personal limit that I would dive on air to in an emergency (think chasing a student on a wall) and that is 170feet.

 

[Doc Harry]

Thanks. I should have been clearer: How do you permanently mark MOD on your stage bottles?

Do you base it on END? pO2? other?

I don't use air below 100 feet d/t narcosis, so should I mark it 100? But what if hand the stage off to someone else in an emergency? Air can be used in an emergency to 190 based on pO2=1.4. So should I mark it 190?

Should I mark the MOD based on my personal preferences or the actual gas characteristics?

I'm leaning towards marking it 190, but that seems a bit silly for a tiny little 14-cubic-foot stage bottle.

 

[Jim Lapenta]

I'd have to go with the actual gas characteristics. But as you stated 190 is 1.4po2. But ever since Jeff's accident last year(he toxed and drowned at 1.3 in a cave) I no longer use 1.4 for the working portions of dives. When doing dives on mix we mix for 1.3-1.35 depending on all conditions. Lake Erie for example- deep, up to 160 feet for me presently- 38 to 40 degree temps- 1.3 it is. And I should have been clearer with my reason for the limit. My limits when using v-planner for example are set to 1.3 and 1.6 for deco at 20 feet

 

[Doc Harry]

I read somewhere recently that GUE was recommending pO2=1.2 for the working part of the dive with a maximum exposure of pO2=1.4

Maybe I'll mark it 155 for pO2=1.2 (air).

I heard about that accident but I didn't get into the details. Tox at pO2=1.3? Scary thought.

I'd have to go with the actual gas characteristics. But as you stated 190 is 1.4po2. But ever since Jeff's accident last year(he toxed and drowned at 1.3 in a cave) I no longer use 1.4 for the working portions of dives. When doing dives on mix we mix for 1.3-1.35 depending on all conditions. Lake Erie for example- deep, up to 160 feet for me presently- 38 to 40 degree temps- 1.3 it is. And I should have been clearer with my reason for the limit. My limits when using v-planner for example are set to 1.3 and 1.6 for deco at 20 feet

 

[DA Aquamaster]

CO2 retention can potentiate an ox tox hit (as well as increase the effects of nitrogen narcosis.)

I still frequently encounter caVE divers who are essentially skip breathing to increase there pentration in a cave and/or decrease their SAC and/or not be the guy who turns the dive on open circuit which results in elevated CO2 levels due to the decreased ventilation and exhalation of the CO2 produced by the diver. Add skip breathing to hard work in a high flow portion of a cave along with an elevated PO2 and you are an ox tox statistic waiting to happen - in addition to the increased impairment due to nitrogen narcois at any given END.

Dropping the average or max PO2 to 1.2 will help but it does not address the real problem - skip breathing and elevated CO2.

The same thing can occur on a rebreather in hardworking situations where the diver may be over breathing the loop with a resulting increase in CO2 levels.

---

The convention is to mark the bottle for an MOD based on O2, rather than N2. Narcosis is addressed by the diver ensuring there is enough He in the mix to achieve the desired maximum END for the mix at the MOD. Going on a gas with an END in excess of 100' on a dive in an emergency will not kill you (directly) but going on a gas with a PO2 above 1.6 can kill you in a fairly short period of time, so that is the number that is most important to know.

I mark my deco bottles for an MOD based on a PO2 of 1.6. I mark back gas and stage bottles with an MOD based on a PO2 of 1.4 - but since the mix varies day to day and dive to dive, the marking is not permanent.

 

[DaleC]

Just to throw a wrench in.

With a 14cuft bottle is marking the pO2 of air (190') the way to go? Would a diver get into more trouble thinking a pony that size is adequate for the depth?
Not a criticism of you Doc, just a thought in general.

On the topic of CO2 retention. It's an interesting topic aand I've given up trying to reduce my sac rate for the time being in favor of increased ventilation to drive off CO2.
Fortunately I don't do dives where I need to worry about how much gas I pack so I just take more back gas or sling a bigger stage and breath well. So many people worry right away about reducing their sac rate without thinking about the risk of CO2 retention as far a toxing and narcosis. From a solo perspective its an interesting risk assessment to do (sac rate vs CO2 retention).
I just figure my SAC will find it's level the more I dive.

 

[rockjock3]

I would mark it for the MOD. If you are using it as a pony then it will be used for bail-out, not the working portion of the dive, so I would use 1.4. That is if I would mark it at all. If it is being used as a pony then it is simply that, a pony. I am gonna have the same gas in it that I am breathing for the dive, which is going to be some kind of recreational mix of gas from normal breathing air up to maybe EAN36. More than likely I would just keep normal breathinig gas in it as it is simply a pony bottle. I would worry about marking MODs if I was using it as a deco bottle, as that is when I really care. If it is bail-out then as long as I can breathe my OC at the depths I am going (and not marking those with the MODs) then why mark the pony when it should be filled with the same gas.

Just my O2

 

[b1gcountry]

I am pretty anal about marking my stage bottles, however, I have a small 19cf bottle that isn't marked. It only has air. You would never have a small stage of backgas for redundancy for any dive involving decompression, so you would never have any deco bottles with to confuse with your pony. If you must, I would say it makes no difference. You should never have that small of a bottle on any dive below 100' unless its labeled argon. Also, once you're solo getting a runaway diver at 170', the pony bottle is about as useful as a spare air.

In my opinion, if you're marking a 14cf bottle for 190', then you're over thinking things.

Tom

 

[ianr33]

If its a pony/bail out tank then I would just mark the mix with a sharpie on duct tape.

IF I was permanently marking it with an MOD then it would be MOD 210. It is after all a MAXIMUM operating depth.

Marking stages with an MOD set for 1.4 and deco bottles with an MOD set for 1.6 just seems too confusing for my little brain.