In addition to being a diver for a very long time, trained by both the U.S. Navy and the USAF, and a diving instructor (NAUI #2710), I have worked in the occupational safety and health, and industrial hygiene, fields for over 30 years before retiring. In the latter career fields, we have what is called a Risk Assessment Matrix, and a Heirarchy of Controls, from a ANZI Z10 Standard for Occupational Safety and Health Management Systems.
We'll talk about the Risk Assessment Matrix first (see below). In the occupational safety and health field, if we have a situation for which the severity is potentially catastrophic, which could lead to death or permanent disability, and the likelihood of occurrence was "Frequent," meaning it was likely to occur repeatedly, it was rated in the "red zone" as "High," and the "Operation was not permissible."
What has been described in the discussion of diving in extremely cold water with a single hose regulator likely to freeze up fits into this "Red Zone" category, and the operation should not be allowed to occur.
In the "Heirarchy of Controls," you will notice that the controls most effective are "Elimination," "Substitution," and "Engineering Controls." The least effective are PPE (Personal Protective Equipment) and "Administrative Controls."
There are differences between different single hose regulators, and some are much more prone to freeze-up than others. This is clearly shown in the International
Polar Diving Conference publication. On page 35 of this document there is an article titled:
SCUBA REGULATORS FOR USE IN COLD WATER: THE U.S. NAVY PERSPECTIVE
John R. Clarke
Navy Experimental Diving Unit 321 Bullfinch Road Panama City, FLORIDA 32407-7015 U.S.A.
This article should be consulted about regulators, and their ability to be used in frigid conditions.
I discussed the possibility of using a current double hose regulator instead of a single hose regulator. This is an "engineering control" which is much higher up on the hierarchy of controls. The double hose regulator has both the first stage and second stage sitting in air, and not subjected to the diver's breath (which is very humid). The
Argonaut Kraken regulator is the only current double hose regulator being manufactured. I have talked with Kraken divers who've used it under ice in the Mid-West/Canada, and they have not experienced freeze-up with this regulator.
I have dived for over 55 years, and had exactly one freeze-up of my single hose regulator. That occurred in a lake on the Oregon coast with a water temperature of 37 degrees in February (winter here). The regulator was a AMF Voit MR-12II, with the Venturi located external to the regulator in a metal tube going to the mouthpiece. To fix that, I did not get a backup octopus, but rather bought a Sherwood Maximus Blizzard regulator, which has heat retention vanes in the regulator. The above report stated this from the U.S. Navy:
From the above regulator rankings, NEDU recommended three regulators be approved for use in cold water. They were the Poseidon Odin/Jetstream (Clarke and Rainone, 1995a), and two Sherwoods (Clarke and Rainone, 1995b), the Maximus and Blizzard. (At the time of our testing, the Blizzard used a heat sink over the exhaust outlet to carry exhaled heat to the lever support assembly; the Maximus did not.)
Perhaps for that reason, we found that the freeze-up susceptibility of the Blizzard was half that of the Maximus. Subsequent to the release of our 1995 report, we learned that the U.S. Antarctic program was successfully using Sherwood Maximus regulators modified with an added heat retention plate within the second stage regulator box, just as had our Blizzard regulators...
...
2004 Results
Category A: Acceptable for temperatures 29°F with minimal free-flow risk.
- Poseidon Xstream.
Category B: Acceptable for temperatures 29°F with minor free-flow risk. - Apeks TX50
- IDI Seaira Spirit Airtec
- Mares Proton Ice Teflon V32 CWD
Caveats
Ice divers should keep in mind the following caveats to NEDU’s regulator testing results, quoted from Layton et al (2004):
• “Testing the same units with different dive profiles, ventilatory rates, regulator adjustment settings, etc., for needs other than those of the U.S. Navy, can be expected to provide different results.”
• “Even when regulators in the “Not Recommended for U.S. Navy use” category are tested under different conditions to determine their suitability for differing needs, those regulators potentially could exhibit acceptable levels of performance.”
This also is an engineering control (using tested regulators for cold water diving).
Redundant air is great, but redundancy with a compromised regulator design in cold water may not be the answer.
SeaRat
