Stage Marking

[Rainer]

Let's pretend a T1 diver wanted to mark a stage (not to be used to extend BT on a T1 dive, but to be used to either get a second T1 dive or a second recreational dive off a single set of doubles), even though this kind or sort of violates his training standards. Let's just call it a fun hypothetical situation. What depth marking would be used for (1) a cylinder that would see a bottom gas for a T1 dive (21/35 or 18/45), and (2) a cylinder that would only see gas for a recreational dive (32% or 30/30), and (3) a cylinder that would see a non-GUE standard gas such as, oh, say 25/25?

Thanks.

 

[rjack321]

Here's how I mark mine although there is NOT a 1:1 relationship between a gas and a MOD:

32% = 100ft
30/30 = 120 (but I wouldn't putz around switching this if I was using 25/25 and the dive was no deeper than 120 anyway)
25/25 = 130
21/35 = 190 (but I may put 18/45 in here if its convenient and I have a 170ft dive planned)
18/45 = 220

I would not actually dive many of these bottom gases gases right up to the MOD label (except maybe 32%). For me there is a buffer between the depths I use the gases and the depths they will want to kill me at. I don't think of the ENDs as part of the "wanting to kill me" depth.

I am not using 21/35 nor 35/25 as deco gasses and if you get these mixed up with your bottom stages you really ought not to be figuring out your marking schema on SB.

 

[Rainer]

Thanks, Richard. Those numbers jive with what our hypothetical diver had in mind. Just funny to have gear marked 190'!

 

[JeffG]

Thanks, Richard. Those numbers jive with what our hypothetical diver had in mind. Just funny to have gear marked 190'!

Mark it for 300' because it looks cool.

 

[rjack321]

yeah this topic has been around awhile

http://www.scubaboard.com/forums/dir-practitioners-zone/208771-mod-markings-stages.html

http://www.scubaboard.com/forums/dir-practitioners-zone/216619-mod-marking-21-35-a.html

When GUE went to a 150ft recommendation for 21/35 everyone (myself included) kinda scratched our heads and pondered how that impacted stage markings for us. I basically concluded it doesn't, there's nothing about a MOD label that says you have to or even want to use it at 189ft.

For my little gaggle of buddies up here marking it 190ft seems to be fine. We know we aren't planning on using it below 160 or so. Not that much different than 30/30 where I probably won't do a square profile on that below 110ft (from O2 concerns) or 25/25 where I would limit my use to 120ft (for narcosis concerns in our less than stellar vis). Basically there's always a bit of a buffer between where you <really> want to be using a bottom gas and its label. At ~30ft, 21/35 just happens to have a bit larger buffer than most. For T1 grads it seems like a big jump I know.