DIVERS SIDE-BY-SIDE comparison tests of regulators have become legendary in the world of diving magazines because, surprise, surprise, we actually take the regulators diving. We normally do these tests in the deep waters of the Red Sea, because the comfortable conditions give us plenty of time in the water.
When it came to comparing how a group of regulators performed in really cold conditions, however, instead of resorting to a bucket of water and some ice, as some other magazines might be (and have been) tempted to do, we went to Sweden in February. The test was carried out as normal, though the dive times were necessarily shorter than had been usual in the past.
The DIVER Group publishes a pair of independent diving magazines in Scandinavia - both called DYK - and Jesper Kjøller, Managing Editor of the Danish edition, provided enormous help in setting things up. He also came with us and acted as stand-by diver, shore cover, and unit photographer.
The project became a combined venture between the Brits and the Scandinavians, between DIVER and DYK.
The format of the tests followed very closely that of previous tests. Four divers, equipped with two cylinders and two regulators each, dived repeatedly in buddy pairs in the same location, replicating exactly the same conditions each time.
In this way, we were able to compare directly the performances of regulators from 13 different manufacturers.
We explained to all the major manufacturers of diving regulators about the coldwater performance we planned to investigate, and asked them to supply us with the single example of their products that they considered the most suitable for diving in rigorously cold conditions.

Out of air
  All but one of the units was of a diaphragm-type design, and most were equipped with either a permanent or optional environmental sealing kit.
We asked that each first stage be equipped with two similar second stages. That would allow us to prove whether the performance of each was up to supplying air to two divers simulating the breathing rate of out-of-air divers.
As usual, AP Valves supplied us with Buddy Tech Wings. They easily provided enough lift for twinned 12 litre steel cylinders and gave us the option of twinning independent cylinders if needed. Banded twin-sets with DIN-fitting manifolds were lent by Oxygene Scandinavia, with air refills from SALT.
It had been minus 15C the night before we set off, driving north from Copenhagen, but we got lucky with the weather as we headed for Swedens west coast. By the time we reached Smøgen, an island set among other islands, and well on the way towards Norway, the weather had turned warm, with an air temperature close to 0C.
It had stopped snowing, and we had to contend with weather no worse than driving wind, hailstones and freezing rain. The seawater temperature was approaching 3C. Was it balmy or were we just plain barmy

Sauna sanctuary
  We did find some comfort between dives. We made camp at the Sea Lodge Sjosportgarden in Smøgen, which gave us the run of comfortable timber-built premises that included an all-important drying room and individual sleeping accommodation; fabulous meals including huge Norwegian prawns and gourmet steaks; hot showers; a hot-tub; and, of course, a sauna.
Most importantly, we were able to find a dive site nearby that had suitably deep water but was protected from rough sea conditions, and could be accessed relatively easily from the shore. This meant that it was quick to get to and from the dive site, and once we had buoyed the spot, we wasted no time getting to the exact same place in deep water twice each day.
Each diver used his own choice of drysuit and thermal insulation. I attracted a certain amount of envy when the others noticed that I was planning to use a Typhoon Icebreaker electrically heated waistcoat on top of my Fourth Element base layer and under my Weezle Extreme undersuit. I relied on Aquion to keep it all dry. The Icebreaker was very effective.

Problems and solutions

The first stage of a regulator serves to reduce the air-supply pressure from the maximum tank pressure (often in excess of 200 bar) to around 8-10 bar more than ambient pressure.
When air is depressurised in this way, it becomes very cold. There can be a drop in temperature of many degrees in the immediate vicinity.
If the surrounding air or water is already very cold, ice can form; and this ice can cause the moving parts of a modern downstream regulator to freeze open. The result is a massive and exponential free-flow of air.
This free-flow usually manifests itself at the second stage, as this is the route of least resistance. If you could shut off the supply to the second stage alone, the problem would probably shift to the alternative second stage (octopus) or even a direct-feed inflator.
The surrounding water may seem very cold, but it will have a lot more heat in it than this air. Water is rarely colder than 0ûC. Its important to warm up the air supply by surrounding it with the small amount of heat that is in the water.
There seem to be two different philosophies regarding regulator design. Some designers of regulators intended for use in cold water try to keep the water away from the moving parts, and this is where the dry-sealed environmental kit comes in.
Other designers try to maximise the flow of water around the moving parts, thus picking up whatever warmth is in the water. Many designs use metal parts in the second stage for the same reason. The metal acts as a heat-sink, keeping the moving parts above 0C. Some regulators have additional metal added in the form of fins or heat-exchangers.
How else can you stop a regulator from icing First, be sure that your air is dry, by having it supplied from a double-filtered source, as is done with nitrox.
The diver can avoid the circumstances that might lead to ice forming by avoiding:
  • heavy airflows while the regulator is in the cold air at the surface before diving.
  • exhaling moist air back into the second stage. Take those all-important check-out breaths while both stages of the regulator are submerged in the shallows, rather than on the shore.
  • jumping in and provoking a free-flow at the cusp between air and water at a time when the first stage is wet but surrounded by the freezing atmosphere. In this case icing is inevitable. This can happen with almost any regulator and the only answer is to turn off the air supply at the tank, submerge it in water, and wait for the ice to melt.
Ironically, it is the regulators that are able to supply the greatest amounts of air, those that breathe the easiest, that are most vulnerable to free-flow due to icing. In the days when most regulators were made of heavyweight metal and had all the breathing characteristics of an asthmatic pensioner running after a bus, icing was rarely a problem.
The trick is to immerse the whole regulator, including the first stage, gently, and to start breathing from it only once it is completely submerged. The /DYK test team dived in water of around 3C, and it was a lot warmer than the weather!

THE TEST TEAMOur test divers were selected because they were tough, experienced and able to cope with the arduous conditions we knew we would encounter.

Soeren Arnvig, 41, Danish. IT consultant by profession, has been diving since 1982. CMAS 2* Instructor, PADI Divemaster. IANTD Mixer/Blender. Married. Lives near Roskilde, Denmark.

Rasmus Sangild, 24, Danish. Student studying for his Masters in Comparative Literature, has been diving since 2000. PADI OWSI. Short-listed for this years Rolex Scholarship. Single. Lives in Copenhagen.

George Brown, 52, Scottish. Civil engineer specialising in underwater structures, a diver since 1969. BSAC National Instructor, TDI Trimix certified, Rebreather (Inspiration) Diver. Married. Lives in Inverness, Scotland.

John Bantin, 58, English. Professional diving journalist, a diversince 1979. BSAC Advanced Instructor, PADI Open Water Instructor, Rebreather Diver (four types). Married. Lives in Twickenham.

Jesper Kjøller, 41, Danish. Managing Editor of DYK, has been diving since 1990. PADI Course Director, IANTD Normoxic Trimix diver. Single. Lives in Copenhagen, Denmark.

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The test
BESIDES GENERAL COMFORT and ease of breathing, which was dependent on the personal opinions of the test divers, we also looked for how useful a regulator might be if it was grabbed in a panic by an out-of-air diver and used upside-down.
We checked for the ease of operation of the purge function and then two divers, using identical second stages from the single first stage, would breathe as heavily and quickly as possible, to test for effectiveness in high-stress breathing.
We normally run independent ANSTI test results alongside our opinions in these comparison tests but, unlike the more simple EN250 testing for the performance of a regulator, EN250:2000 testing to Cold Water standards using an ANSTI breathing-machine is a time-consuming and hence very expensive process.
We estimate that it would cost nearly£20,000 for an independent test of the regulators from our comparison test, which is why we decided not todo one.
However, all the regulators supplied for the purpose of our comparison test had CE type-approval to that standard. Among the criteria set out for such a test is that the water be of a temperature in the range of 1 to 4C.
The regulator should be able to provide sufficient air at 25 cycles per min and 2.5 litres per stroke at a depth equivalent of 50m (6 bar), with exhaled air at a minimum humidity of 90%. Supply air pressure should be 50 bar.
The regulator has to be rigged both as if the divers head was upright and also in a horizontal, face-down swimming position.
The maximum allowable work of breathing is 3 joules.

BRA: Some regulators have a Breathing Resistance Adjustment controlled by a knob on the side of the second stage. It alters the amount of inhalation effort needed to initially crack open the valve and allow the air to flow on each inhalation. It does not affect the volume of that flow. Different manufacturers use alternative designations for this feature.

Bypass tube: Mares regulators have a bypass tube that directs the main flow of air from the second stage valve to the mouthpiece, bypassing the back of the front diaphragm and avoiding the need for the venturi control.

Environmental sealing kit: Often supplied as an optional extra, this keeps the working parts of the regulator first stage separated from the water and normally transfers water pressure by means of a flexible plastic diaphragm. Although often associated with coldwater diving, the primary purpose of an environmental sealing kit is to keep out impurities such as grit and sand that might be mixed with the water in which the regulator is being used. Many of the regulators tested were permanently dry-sealed.
Heat-exchanger: Metal inserts (often in the form of fins to maximise their surface area) that allow an interchange of heat to the air supply from the surrounding water.
High-pressure port: Supplies gas at tank pressure for a pressure-gauge and/or integrated computer.

Medium-pressure port: Supplies the primary regulator second stage, alternative second stage, BC direct-feed hose, and drysuit direct-feed hose (when needed).

Universal joint: Positioned between the hose and the second stage, this allows the hose to take a route that avoids pulling uncomfortably at the mouthpiece. However, it has been found that in some cases such a universal joint can reduce a regulators ability to supply the maximum amount of air.

Venturi Plus/Minus (or Dive/Predive): Second stages are designed with such a clean flow of air that a venturi effect is produced. Unfortunately, this can cause a reduction of pressure directly behind the pressure-sensing diaphragm, causing it to be sucked in, increasing that air-flow exponentially and causing a free-flow. This happens mainly at points of greatest pressure difference, such as are found between the air and the water at the surface. The Venturi Adjustment Lever operates a flap or vane that disrupts the air-flow (destroying the venturi effect) temporarily within the body of the second stage. It is used pre-dive.