OP
MOD marking for 21/35
- Thread starter rjack321
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OP
OP
You all are big boys and girls and can make your own decisions about risk... Do you fancy this enviroment as pretty stable? The rough guideline has historically been 90mins immersion for deco dives in the ocean due to the potential for changing conditions (currents, weather, boat traffic/shipping, etc.)
Locally we also have a group going way over that, but I'm not diving with them and can't really comment on their thoughts in this regard.
jjones9527
Contributor
We are still relatively close to shore. We don't go any farther than we can be towed or swim back, and do it in teams of 3 for added redundancy. There are many different areas where we do dives like this, but the deepest average depth we are doing is about 70'. Using 32% as a bottom gas and O2 for deco we're only getting about 20mins deco time. The St Lawrence River gets up into the 70's in the summer as well, so immersion isn't really an issue.
But that is what you do every time you choose a back gas. Diving the Jodrey I could go down to 240' if I wanted, but training and experience says I only go to 170', so I choose my back gas accordingly. There is no hard floor to keep me from going any deeper. As for labeling 32% for 120, its no more dangerous than 35/25 wrt PP02, which brings us back to whether or not we want to factor in END as part of the MOD, or keep within a PPO2 of less than 1.6.
But that is what you do every time you choose a back gas. Diving the Jodrey I could go down to 240' if I wanted, but training and experience says I only go to 170', so I choose my back gas accordingly. There is no hard floor to keep me from going any deeper. As for labeling 32% for 120, its no more dangerous than 35/25 wrt PP02, which brings us back to whether or not we want to factor in END as part of the MOD, or keep within a PPO2 of less than 1.6.
OP
Gotcha
Good point. To me this all springs from the apparent shift from average ppO2 of 1.2 to max 1.2 It not so much about which gas whether 32, 30/30 or 21/35. The latter 2 have "new mods" and its not clear if people are just diving them at the new MODs or both diving and marking them at the new MODs. More than a few folks still dive 30/30 to 120ft so its certainly a source of inconsistency.
dsteding
Contributor
One of the concepts I've heard in some GUE-trained circles is that bottom stages with the same gas as your backgas do not have MOD labels, only deco bottles do. Not sure how widespread this practice is, or whether it has any validity, but thought I'd toss it out there.
OP
Yeah we bantered that around a few pages ago. Basically that logic applies when you only have one on a deep dive and start off breathing it at the surface.
Once you're on a boat with all sorts of stages kicking around, some which might be used for dive 1 and some with a shallower mix used for dive 2 the "don't bother marking them" argument loses some steam.
You start to need a waterproof in-water backup to the analysis tape IMO. Ditto if you have a couple of bottom stages and a deco bottle like Jeremy is using. Ie. the absence of markings is a poor way to ID gas.
DeepSeaExplorer
Contributor
JeffG
Contributor
Thats what I have done. I know of another guy that put a 300ft Mod sticker on his stage to make it look "cool" for video.
For the open water dives we do (non-multi stage), we beath the stage first and breath it till it is empty. So unless you break the mod for your bakgas, you are not going to break the mod for the stage.
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