I'm not so sure the issue's as big as some folks make it out to be.
I dive Puget Sound regularly, as well as Vancouver Island, Lake Washington and occasionally Lake Crescent. My regs are Scubapro MK25's, which are not environmentally sealed ... and I've never experienced a freeflow.
I don't think it's much of a concern till you start diving in water a bit closer to freezing than the low 40's we typically get here in winter, as long as you keep your regs properly cleaned and maintained.
... Bob (Grateful Diver)
Well the MK25 is exempt from the conversation because it too is a Cold Water regulator. But the technology there is patented and when you're talking outside the Scubapro world the enviro seal is what makes the difference....
From the scubapro MK25 website...
//**** From Scubapro *****/
Diving conditions can be drastically different, including extreme cold water and outside temperatures, posing the possibility of a regulator "freezing." Therefore, resistance to freezing is imperative for the diver. SCUBPRO regulator systems are CE approved for 4300 psi cold water diving. Some models go even beyond this super stringent qualification and have successfully been tested in extreme cold diving conditions at less than 36 degrees Fahrenheit. As a specific anti-freezing measure, SCUBAPRO enginers have designed a patented finned cap for both the MK17 and the MK25 first stages for optimal cold water diving. The ribs act as a radiator to increase the surface area of heat transfer from the water to warm up the internal parts that have been drastically cooled down by the gas pressure drop.
/***** End of Scubapro's quote *********?
The Mk25 is a much better regulator than the ones I dive, because I can't afford the MK25, but if I could afford it I would give up enviromental seal in a heartbeat, but if that isn't in the mix and I'm looking at aqualung, oceanic, cressi regulators then I'm going to want it to be enviromentally sealed. And while I couldn't find it on the scubapro website and
I lurk this board a lot and know that NWGratefulDiver knows his stuff and have a lot of respect for him, but a MK25 is the Cadilac of regulators and I would say that it would not be prudent to think that because a MK25 doesn't freeze up at depth in Lake Crescent that an Aqualung Titan would act the same way.