Prebreathing Survey

[doctormike]

Many units with offboard dil can't really be prebreathed out of the water. It is too heavy to put my cave bailouts/dil on and walk. I can put the loop in my mouth and jack up the O2 content in there. But I can't check the wing, dil MAV, ADV, and sometimes not even the drysuit until I'm geared up in the water.

Yup, that's what I was realizing. This is the benefit of reading SB with an open mind - often we get very comfortable with our own practices and don't realize that there are other scenarios that we aren't familiar with that change things completely.

I think that the main thing to check is that the unit can maintain a breathable loop. Everything else can be checked in the water - if your wing or ADV doesn't work on the surface, you can fix it before descent. It's more convenient for me to do everything together in my rig for boat diving, but I can certainly see how that might not work for cave divers.

 

[OceanEyes]

OK, so you do a 5 minute prebreathe, unless you are on a liveaboard, in which case you perform a prebreathe of unspecified duration? And if the seas are calm, you prebreathe while driving?

Prebreath on a liveaboard is 5 minutes, either on the dive deck or aboard a tender as the situation warrants.

Can’t say that I’ve ever done a prebreath while driving a boat or a car, though the odds are favorable that someone around here has done both. If you’re not familiar with some of the driving practices common on Florida roads and waterways, (which include activities such as, ((though certainly not limited to)), texting, eating, make-up application, consumption of meals and adult beverages), such behavior by a driving diver would not seem overly bizarre in comparison.

 

[doctormike]

Can’t say that I’ve ever done a prebreath while driving a boat or a car, though the odds are favorable that someone around here has done both.

I once went on surface O2 while driving! Heading back from the local quarry and I was a little achy. Didn't really think that I was bent, but I had my deco bottle with me, so...

 

[jstrang]

I prebreathe my JJ for a couple of minutes. Enough time to confirm what my voltage on the solenoid battery is and confirm that the solenoid will hold a set-point: I have had 1 occasion where the solenoid was leaking and the set point would slowly rise up. Ended up being an Oring attachment going to the solenoid.

 

[PT4476]

I breathe mine for a few minutes after building it, let the solenoid maintain set-point, check solenoid battery, let rms run up until it reads 45 minutes rct (if the rms is working) see how the cells are tracking. Shut down O2 confirm that cmf is working… Do another similar check on the bench before the dive.

 

[stuartv]

Yup, that's the link in my OP!

Doh!! Reading is FUNdamental!

 

[rjack321]

Yup, that's what I was realizing. This is the benefit of reading SB with an open mind - often we get very comfortable with our own practices and don't realize that there are other scenarios that we aren't familiar with that change things completely.

I think that the main thing to check is that the unit can maintain a breathable loop. Everything else can be checked in the water - if your wing or ADV doesn't work on the surface, you can fix it before descent. It's more convenient for me to do everything together in my rig for boat diving, but I can certainly see how that might not work for cave divers.

The lack of wing/inflator was one reason I went back to onboard dil/wing gas for boat diving. I can gear up with my "cave" rig while bobbing in the water next to my boat (assuming I dont drop a cylinder) but I didnt like backrolling in with no wing and no dil at all. Onboarding my dil/wing gas made much more sense. In a cave like Hole in the Wall with a ton of sawtoothing even an onboard 4L tank is marginal so offboarding makes much more sense there. And for a cave like that I am only gearing up in 6ft of water, so if I accidentally end up with an empty wing its not like I sink into the abyss with only a loop full of O2 in my mouth.

 

[kensuf]

I once went on surface O2 while driving! Heading back from the local quarry and I was a little achy. Didn't really think that I was bent, but I had my deco bottle with me, so...


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Pinch your nose when you do that, it'll work better.

 

[doctormike]

Pinch your nose when you do that, it'll work better.

Yup. Or do this. Martinis help with offgassing. I think that's what "Martini's law" means...

 

[OceanEyes]

Pinch your nose when you do that, it'll work better.

You could use a clothes pin to pinch your nose. If you use your left hand, you won’t be able to access your turn indicators, so you’d fit right in here in Florida.