Prism 2 standard procedure upon ascent

[hedgercm]

I dive a unit other than the P2 but dive with other P2 divers. During our last dive one of the divers shut off their dil (via slide switch) upon turning the dive and commencing the ascent. My question is: Is this standard practice? I am not in the business of telling others how to dive their unit but would like to know for my own edification.

 

[davehicks]

Following. This seems nuts. Curious if there is a rationale for this. I assume/hope they had separate inflation gas???

 

[hedgercm]

Following. This seems nuts. Curious if there is a rationale for this. I assume/hope they had separate inflation gas???

Suit gas is separate and wing inflation is separate so just the ability to add Dil to the counter lung was impacted.

 

[rongoodman]

Not something I remember from my training on the unit.

 

[kensuf]

Was he just shutting off the ADV, or all DIL addition?

 

[Dsix36]

Shutting of the ADV before ascent is rather common if diving a hypoxic diluent regardless of what unit is being used.

 

[211ratsbud]

I've heard quite a lot of instruction showing people to disable adv features once on bottom - the rest of it totally uncertain.

I wasn't taught that.

 

[ToneNQ]

It's not standard, but when diving a deeper helium mix it is something I do. Not on the turn, though you easily can, but on ascent.

Once you hit the bottom, trim out and get the loop volume stable at 1.3 set point, you won't use your ADV at all. When you're at 6m using the unit in O2 mode, you don't want a high helium Dil being added to the loop when you O2 flush. I have an inline isolation valve at the ADV, and I've seen a lot of units with one fitted. Not standard, but common enough when you look for it.

I've met guys that don't use their ADV at all, they run entirely on the Dil MAV. Not my style, but I'm about 1000 hours short of giving those guys any advice. It's not taught, just something I figured was useful after a bunch of Mod 2 dives. When you have an 80min ascent with stops, you get a lot of time to ponder. Using air diluent you wouldn't bother, but at remote locations when you're paying 30c/L for Helium and 15c/L for O2, you don't waste it. Additionally, at locations where you can only get O2 at 93%, the last thing you want is dilution.