Use a gag strap?

[stuartv]

Really? I do loose lips when I do an O2 flush at 20 feet to check for current limitation. If you just bite the mouthpiece wings and relax your mouth, it doesn't leak?

Maybe Pete is right about the rEvo...

Correct. If I totally relax my mouth and try to exhale out of my mouth (while in horizontal-ish trim), my breath just goes through the loop. To vent, I have to go somewhat head up.

theoretically that may be correct but on dive of 8.5ata im hoping you'd stop for deco wouldnt that allow the cmf valve /solenoid to "catch up" to whatever set point you had

The CMF won't catch up. It only puts out enough to replace what you metabolize. So, other than descending, the CMF by itself is not going to cause the PO2 to go up. But, the solenoid should ensure it doesn't go hypoxic. Otherwise, a manual add of O2.

But, yeah, from 250, I imagine if you go straight to the surface with no stops, going hypoxic near the surface may not be your biggest concern. And in the example given, the mix would only go hypoxic at around 8' depth, I think? At 8' it would be ppO2 of 0.16?

So, even one burst of O2 into the loop somewhere along the way up (from 250) should be enough that the loop won't go hypoxic at all, right?

I think the primary risk is that you get shallow, vent too much from the loop and then the ADV fires. Depending on the location where the ADV injects gas into the loop, it might not mix with the other gas in the loop adequately before you breathe it and so then you could inhale a good breath or two of hypoxic gas. I think on the rEvo the location of all the gas injection (i.e. before the 1st scrubber) makes this unlikely. But, other CCRs have the ADV injecting just before the DSV or right into the inhale counterlung. Then it seems like it could be a problem if the dil is hypoxic.

 

[Dsix36]

How many of us are using really low fO2 BO on a regular basis? I use 15/55 fairly often, I don't have an issue connecting that to my BOV starting on the surface. You can breathe that on the surface (like a freight train) but you aren't going to actually pass out for quite some time. Plenty of time to close the BOV and breathe the atmosphere.

Vs 10/70 BO into my BOV makes me nervous.

I use 10% mix almost exclusively unless i am going deeper. this way i can always jump a deeper wreck if the conditions warrant. I know that not every one does this though. it scares me to have this to a BOV above 20'

 

[rjack321]

I think the primary risk is that you get shallow, vent too much from the loop and then the ADV fires.

If the O2 is off or empty
Or you metabolize the loop down on or near the surface without the ADV being isolated
You're in big trouble either way

Which is why ONLY putting O2 in your loop on the surface and isolating your ADV are so important.
Unless you have a Revo with a terrible ADV that barely works on the best of days lol

 

[rjack321]

I use 10% mix almost exclusively unless i am going deeper. this way i can always jump a deeper wreck if the conditions warrant. I know that not every one does this though. it scares me to have this to a BOV above 20'

I commonly use hypoxic dil (10/50 or similar)
But rarely plumb hypoxic BO into my BOV. I think I have used <15% BO maybe a half dozen times. I don't plug an alternative gas into the BOV I partially deploy my 50% second stage. So if I have to bail shallow I go to the 50% instead of the BOV.

 

[lermontov]

If the O2 is off or empty

Which is why ONLY putting O2 in your loop on the surface and isolating your ADV are so important.
Unless you have a Revo with a terrible ADV that barely works on the best of days lol

how do you isolate the adv on the Revo unless you turn off the tank -im assuming other ccr models allow you to stop the adv feeding the loop and keep the wing supplied ?

 

[rjack321]

how do you isolate the adv on the Revo unless you turn off the tank -im assuming other ccr models allow you to stop the adv feeding the loop and keep the wing supplied ?

I dont know, I dont own a revo. My understanding is the revo adv is so bad nobody uses it

 

[stuartv]

Yeah. Basically, there is no way to isolate the ADV on a rEvo (AFAIK). But, it’s okay because we keep them tuned so stiff it never fires unless we really, really mean for it to.

I CAN pull in gas via my ADV, but now that you got me thinking about it, I realized that I never do. I always use the manual add to get dil into my loop.

 

[lermontov]

Yeah. Basically, there is no way to isolate the ADV on a rEvo (AFAIK). But, it’s okay because we keep them tuned so stiff it never fires unless we really, really mean for it to.

I CAN pull in gas via my ADV, but now that you got me thinking about it, I realized that I never do. I always use the manual add to get dil into my loop.

i cant say i have any issues with the adv - though i have experimented with it in different positions and seems to work ok so far

 

[Germie]

The ADV on my Inspo works really well. The ADV on my Sidekick does not provide enough gas at depths over 30m.
I have tried a lot of different things. The BOV from Inspiration is too heavy after a couple of hours diving, so I stick with the DSV. When scootering it is way much to bulky. The DSV is fine. I can close my adv of my sidekick and inspo really easy myself with a flowstop. I have tried a gagstrap as I wrote, but it is not my thing. I prefer to dive without. If you use the Inspo with Sidekick as BO ccr, the gagstrap will be in the way. I believe only Revo has a gagstrap when you buy it (and most people I know take it off asap). Maybe there is a little bit more safety, but if you loose consiousness during a dive, a gagstrap will not help. If it holds the loop without flooding it is too tight. If you use it comfortable, it is too loose. So I don't believe in real extra safety. I don't think it is wrong to use it, but happely it is optional.
It is one of the optional things in my eyes with a lot of personal preferences. There is not 1 best way.
For my Sidekick I use the Revo block for manuall adds.

 

[cathal]

Agree. That's sad. Hyperoxic seizure? If so, another failure mode that might be addressed by a gag strap. Not just (hypoxic) LOC.

Completely agree, to no matter what the triggering event is, once water gets in the airways there's no chance of survival. The gag strap prevents this.