ice particles from MK25?

[FFMDiver]

Diving cold water with my new SPMK25 and ice landed on my tounge.
Assuming it was getting frosty I quickly stuck in my Xstream (on an H valve).
Now I understand why people love em. But my question is, where does frost
come from? Is it the second stage seat?

 

[Bob3]

Yep, the adiabatic cooling condenses & freezes water vapor on the innards, little pieces fly off & gives that refreshing blast.

 

[DA Aquamaster]

The plastic air barrels in the current SP second stages are very poor conductors of heat. With the older chrome plated brass second stages with metal air barrels heat transfer was excellent and the relative warmth from the surrounding water would be transferred into the second stage and prevent ice from forming in the air barrel.

The same effect occurred to a lesser but still effective extent with the metal air barrels used in the G250 until the last couple years.

A pleasant side effect of this was that moisture form your exhaled breath would condense on the metal air barrel and thenhelp moisturize air during inhaltion which went a long way toward preventiing dry mouth.

 

[FFMDiver]

makes complete sense.
Thanks folks.

The plastic air barrels in the current SP second stages are very poor conductors of heat. With the older chrome plated brass second stages with metal air barrels heat transfer was excellent and the relative warmth from the surrounding water would be transferred into the second stage and prevent ice from forming in the air barrel.

The same effect occurred to a lesser but still effective extent with the metal air barrels used in the G250 until the last couple years.

A pleasant side effect of this was that moisture form your exhaled breath would condense on the metal air barrel and thenhelp moisturize air during inhaltion which went a long way toward preventiing dry mouth.

 

[donacheson]

Yep, the adiabatic cooling condenses & freezes water vapor on the innards, little pieces fly off & gives that refreshing blast.

Which leaves open the question: Where does the water come from?

An Al80 filled to 300 psi at 75F SHOULD contain only about 1/4 gram or about 1/2000th of an ounce of water vapor. If that's all there is, it's hard to believe that a noticable portion of that would condense, accumulate and break off.

I'm guessing that a sloppy fills over a period of time have led to an accumulation of water in the tank which COULD then lead to an appreciable accumulation on the innards of the reg at the end of a dive when the tank pressure is low.

 

[Jonny_Rocket]

Isn't it moisture from breathing, not water (from the tank or otherwise) that condenses inside the second stage?

 

[Doc Intrepid]

correct

 

[Rick Inman]

Isn't it moisture from breathing, not water (from the tank or otherwise) that condenses inside the second stage?

correct

So ...the air you breath in is moisture free?... And then you pick up the moisture while the air is passing through your breathing system? From where? Not in the lungs, I would think. Then, from in your mouth and throat (saliva)?
So basically, the frozen chips are a spit spritz?
Suck on that.

 

[OE2X]

Thanks Rick for giving me more info than I needed. Remind me to invite you over to this side of the hill and not bother going diving in your neck of the woods.

 

[scubatoys]

So ...the air you breath in is moisture free?... And then you pick up the moisture while the air is passing through your breathing system? From where? Not in the lungs, I would think. Then, from in your mouth and throat (saliva)?
So basically, the frozen chips are a spit spritz?
Suck on that.

Yea, from your lungs. The lungs moisturize the air to 100% humidity with each breath, this is why you are so dehydrated after a dive, you are giving up a lot of moisture with each breath.... Not just scuba spit... (is that a phrase??)