Rec Vs. Technical???

[Tony387]

120 ft on 36%...really? Wow.

 

[tursiops]

If he goes to 120 on 36% then deco will be the least of his worries.

 

[Dr. Lecter]

I mean, you could...there are any number of things I'd call more risky than a 1.66 working ppO2...but it's not a good idea. You're shallow, so unlike a deep air dive (like 240') you don't get the same narcosis that might otherwise help protect you (emphasis on might) from a CNS hit, and you might be at it for a really long time, versus the shorter exposure time of a deep air dive with a similar or even higher ppO2. NOAA would say you have less than 45 minutes of exposure at that ppO2, and you're not taking air breaks like you would on deco...FWIW, even VPM-B 0 puts you slightly into deco if you roll in the sand for 20 minutes breathing 36%, so O2 clock might not be as much of an issue.

You're also presumably working, so you're not at rest like you would be for a deco hang at 1.6, and you're possibly colder depending on the bottom temps.

Overall, not a good plan...but it probably won't kill you, at least not right away. But emphasis on the probably.

 

[CptTightPants21]

Don't do that.

Let me know when you figure out why!!

People need to do some math. While it is aggressive and I don't recommend it, it is only a PPO2 of 1.67.

At this point this thread has covered what can/needs to be done and it is up to the OP to decide what to do.


Frankly I think you have 2 choices. 1) You dive doubles with an understanding that there will be ~longer~ deco time without using pure O2 or 2) get AN/Deco procedures which will allow you to dive a larger single tank with a pure O2 bottle for deco. Anything besides these options is pushing your air supply and/or PPO2.

 

[Dr. Lecter]

Where does rec really end and Tec begin? My thought before was once you hit a deco stop you have exceeded recreational diving. But now I think of it as multi gas. Or more than a short deco?

There's an easy defining line: if you're suddenly unable to take another breath off your reg at any point in the dive, can you immediately go to the surface without "risking" DCS? If so, you're doing rec diving...yes, you still might get bent but according to whatever dive algo you're using, you shouldn't be.

If not, even though the risk is "smaller" with short decos (and one algo's short deco might be another algo's last minutes of NDL), you're doing tech diving. It means that when you go to take a breath and don't get one, your only reaction is gee, that's weird but whatever...and then you get on with your dive using the gear and training necessary to solve all problems underwater while still completing required stops/travel before ascending.

 

[tursiops]

a couple people here have said you can easily do 120 on 36% nitrox for 30 min

I just went back and reread the entire thread. I find NO post that says you can do this.

{added} except the very recent ones that point out you are risking oxygen toxicity by doing that

 

[Octopusprime]

People need to do some math. While it is aggressive and I don't recommend it, it is only a PPO2 of 1.67.

At this point this thread has covered what can/needs to be done and it is up to the OP to decide what to do.


Frankly I think you have 2 choices. 1) You dive doubles with an understanding that there will be ~longer~ deco time without using pure O2 or 2) get AN/Deco procedures which will allow you to dive a larger single tank with a pure O2 bottle for deco. Anything besides these options is pushing your air supply and/or PPO2.

No doubt I would not do it past 90ft I have only done nitrox when doing multiple 40-60 ft dives

 

[dumpsterDiver]

People need to do some math. While it is aggressive and I don't recommend it, it is only a PPO2 of 1.67.

At this point this thread has covered what can/needs to be done and it is up to the OP to decide what to do.


Frankly I think you have 2 choices. 1) You dive doubles with an understanding that there will be ~longer~ deco time without using pure O2 or 2) get AN/Deco procedures which will allow you to dive a larger single tank with a pure O2 bottle for deco. Anything besides these options is pushing your air supply and/or PPO2.

OR.. you read up on it a little, buy a high pressure 149 cu-ft tank, fill it with some nitrox of the appropriate flavor, clip a 30 or 40 cu-ft bottle off as a bailout bottle (full of air) and keep your deco under 15 minutes or so.

EDIT: then again, if you are using nitrox for 40 ft dives, then maybe this isn't for you?

 

[Octopusprime]

Sorry rivers said 32% for 30 min

 

[Dr. Lecter]

OR.. you read up on it a little, buy a high pressure 149 cu-ft tank, fill it with some nitrox of the appropriate flavor, clip a 30 or 40 cu-ft bottle off as a bailout bottle (full of air) and keep your deco under 15 minutes or so.

EDIT: then again, if you are using nitrox for 40 ft dives, then maybe this isn't for you?

DD's option is real, but it only works if by nature or nurture (formal training, informal mentoring, and/or online browsing) the diver really gets that they have to use the bailout when the SHTF, and stay the down to finish their deco no matter what's going on in their head. Of course, I'm not sure how assured even the most formally trained new tech diver is of that...but mindset is still necessary, even with an AL40 full of honeybadger gas.

---------- Post added February 4th, 2015 at 08:22 PM ----------

Sorry rivers said 32% for 30 min

Uh, not at 120' if it's supposed to be NDL.