sharing air in cold water

[scuba andy]

Hi,
Was at a 20m deep quarry last weekend and because the water was 4^C I saw 2 x freeflows in the 2 days I was there. Its not a suprise to me knowing that cold water lends itself to regs freezing up.

But on the 2nd freeflow at 16m the diver went to airshare with a buddy to the surface. And it occured to me that the extra demand of 2 x divers on the same 1st stage could potentially have resulted in the 2nd set of regs to freeze and freeflow too.

I know there were other potential options in the above freeflow situation at 16m (sipping air & CESA from 9m if necessary, cracking the cylinder valve on and off as needed, etc).

But my question is: during a situation where one person is out of air completely and has to share air with a buddy in cold water, is there a way to minimise the chances of the air-shared set of regs from freezing on ascent?

 

[eponym]

Excellent question!

Step one would be using regsets appropriate to the conditions. I have seen at least a dozen freeze-up freeflows in similar conditions, and most of them were due to regs that were not designed for those temperatures. Most were also without the added demand of a second diver breathing on them.

Some other thoughts:

Buddy breathing would help, but is not commonly taught nowadays, at least in my experience in the USA.

The donating diver could take a breath before starting the share, and then slowly exhale as long as possible, in hopes that the needing diver can calm down and reduce his breathing rate.

And you wouldn't want to touch that power inflate button right away.

Constant practice on everyone's part with air sharing might mean less stress when the real thing happens, hence lower consumption rates.

-Bryan

 

[TSandM]

I think those situations are the ones where you ought to be thinking long and hard about redundancy. Whether it's a pony bottle or a set of doubles, I think it's a good idea to avoid a double draw on a single first stage. This is one of those things where planning prevents problems.

 

[rx7diver]

scuba_andy,

A Y-valve is perfect for this type of situation: one first stage would be for the primary reg and the drysuit, and the other first stage would be for the backup reg and the BCD.

Safe Diving,

rx7diver

 

[Diver0001]

Hi,
Was at a 20m deep quarry last weekend and because the water was 4^C I saw 2 x freeflows in the 2 days I was there.

I find this an extremely high incidence of free flows due to freezing regulators. I've been diving in *very* cold water for many years and I've seen exactly ONE regulator freeze open during a dive due to the cold. They often freeze open during equipment set up or entry into the water but very seldom during the dive.

I would also say that using dual valves (an H or a Y valve or fully redundant twins) solves all of the other problems you mentioned.

R..

 

[kirasir]

I find this an extremely high incidence of free flows due to freezing regulators. I've been diving in *very* cold water for many years and I've seen exactly ONE regulator freeze open during a dive due to the cold. They often freeze open during equipment set up or entry into the water but very seldom during the dive.

R..

Happens quite often here in the Great Lakes. Arabia wreck, up in Tobermory Ontario, is known for its share of fatalities and DCI incidents some of which were caused by free flows: 30+ meters and fresh water at usually less than 5C degrees in the summer.

Personally, my rule of thumb is anything colder than 10C and deeper than 20m means I'm diving two tanks. Why risk it?

 

[Diver0001]

Agreed.

Our winter diving involves typical water temperatures in the 2C range. Coldest I ever registered on my computer was -2C (which caused spontaneous and uncontrollable swearing and we capped the dive at 30 minutes)

But ok... despite that, we seldom see free flows once the dive has started. 90% of all the frozen regulators I've seen in these conditions happened during entries.

R..

 

[TSandM]

The only freeze-induced freeflow I've had was about 30 minutes into a dive, but it was set up by an air-sharing drill (thus doubled demand on my reg) and finally set off by the backup reg freeflowing when I dropped it . . . and then it wouldn't stop. Water temp was in the mid 40's (what, about 6C?) and air temperatures that day would probably have been somewhat similar.

 

[scuba andy]

Thanks for your comments.

With reference to the queries on high incidence of FFs: the 1st free flow was on-the/near-the surface while practising skills. Turning off my buddies cylinder for a couple IDF minutes allowed the reg to thaw. The 2nd free flow another persons regs which started at 16m as mentioned already.

Eponym, I think I'll put buddy breathing training on my to-do list. But do you think that drawing air when your Buddy is visibly exhaling (and visa versa) from the octopus might work as an equivalent measure?

A pony for redundancy seems a good option to have available. Is it standard equipment for most diving cold water?

Cheers

Andy

 

[rhwestfall]

A pony for redundancy seems a good option to have available. Is it standard equipment for most diving cold water?

for me it is.....