Did I make a mistake regarding proper procedure? No safety stop after 1 min at depth.

[Mr Carcharodon]

To bubble you have to have some gas to make bubbles in the first place. After the first dive on nitrox you had something like a third of the critical volume of gas and even less so after the surface interval. On the second dive you were not down very long so you are right that if you are not down long you will not absorb much nitrogen and will have low risk. Since "not long" is vague there are those who will say in the face of fuzzy information always to do a safety stop. But that gets pretty silly sometimes this being one. At shallow depths there just is not enough nitrogen to worry about no matter how long you stay. 45 feet is not there, but close. Regarding the comments about time most DCS cases show up in an hour or two. Twenty four hours is way out on the tail of the curve but does happen...rarely.

Just so you worry less you could do a minute stop at 10 feet.

 

[Frosty]

the "right " thing? probably not uber smart. But think about all the Instructors with multiple students.
how many times are they conducting Cesa from 30 feet ish?

 

[doctormike]

To bubble you have to have some gas to make bubbles in the first place. After the first dive on nitrox you had something like a third of the critical volume of gas and even less so after the surface interval.

But that's the thing, the "critical volume" of gas is an empirically derived guesstimate that is accurate for the vast majority of the bell curve. One thing that I have realized is that there is a lot of stuff under that bell curve that most people are lucky enough to never see.

Divers do bubble, even staying way inside NDLs, as can be easily documented by doppler. Now most of those people don't get clinical DCS, but you need a lot less inert gas loading to bubble than you might think. Most of those bubbles are filtered out by the lungs and are harmless, but there is also a lot that isn't known about why some people have clinical symptoms and other's don't (the role of shunts like a PFO, personal susceptibility factors, etc).

Also, according to the bubble pumping theory, things like multiple ascents and fast ascents increase your DCS risk even though you have less than the "critical volume". So the new divers shouldn't get the idea that as long as I have less than X amount of inert gas loading, there is nothing that I can do to get a hit.

And of course, it's not really a volume, it's a question of overpressure in separate compartments, so bubbling is dependent on your profile, not just the total amount on-gassed, otherwise tech diving or saturation diving wouldn't be possible.

 

[DivemasterDennis]

The length of the surface interval impacts how much no decompression time you have on the second dive. The longer the surface interval, the longer your NDL. On every NDL profile a safety stop is a good idea, but not mandatory. Try and stay in the habit of doing one on every dive over 7 meters or 20 feet. BUt as to the OP's original question, I think he was fine with I will call the profiles on his three dives. His is a reason I always check NDL time against the tables on repetitive dives, just to confim my computer's readouts.
DivemasterDennis

 

[Texasguy]

Safety stop is what it is, safety. It doesn't stand for decompression. With that in mind, any recreational dive can be done without a safety stop. It adds a margin for safety but not mandatory per se. It is like looking both ways when you have a clear green signal, helps but as extra protection.

 

[Diver0001]

Excuse my ignorance, what do you mean by that?

He means he's a troll who is trying to make you feel insecure for his own amusement.

You'll be fine. Your first dive was no where near the NDL and even if you made those two dives back to back without a surface interval then you would have been fine at the point where you made the ascent. You should be able to read this from the tables, if you learned them.

That said, once a dive starts I would find it highly unusual for a buddy to want to return to the surface because they forgot something. My thinking would be more like "remember it next time". YMMV

R..

 

[Texasguy]

That said, once a dive starts I would find it highly unusual for a buddy to want to return to the surface because they forgot something. My thinking would be more like "remember it next time". YMMV

R..

Unless it is a tank or extra weights...

 

[RJP]

Unless it is a tank or extra weights...

Unlikely you'd get to the bottom without either of those.

 

[doctormike]

Safety stop is what it is, safety. It doesn't stand for decompression. With that in mind, any recreational dive can be done without a safety stop. It adds a margin for safety but not mandatory per se. It is like looking both ways when you have a clear green signal, helps but as extra protection.

You'll be fine. Your first dive was no where near the NDL and even if you made those two dives back to back without a surface interval then you would have been fine at the point where you made the ascent. You should be able to read this from the tables, if you learned them.

Again, remember what we are doing when we draw that "bright line through a grey area". Words like "mandatory" imply that DCS stress and risk of injury follow some specific law that you either follow to the letter and therefore are safe, or violate and get a hit. It's simply not like that. All that tables and algorithms do is let you reduce your risk to acceptable levels, but even the Petrel 3 won't know what's going on inside your body.

You absolutely can get bent within NDLs. You absolutely can blow off a bunch of deco and survive without injury.

We do our best to strike a good balance between safety and utility.

And once more, I don't think that the OP is likely to have been injured. But the theoretical discussion is important for new divers reading these threads.

 

[Storker]

Divers do bubble, even staying way inside NDLs, as can be easily documented by doppler.

And the amount of bubbles varies dramatically from person to person.

I listened to a presentation the other day, with data from a study that several of my clubmates participated in. They did a moderate chamber deco dive and was monitored for bubbles with ultrasound imaging for (IIRC) up to about three hours after the dive. The amount of bubbles detected varied from practically none at all, to significant amounts for more than three hours after reaching surface pressure.

The data are currently being written up for publication. I guess the paper will go to peer review some time during this year.