Breath In - Breath Out

by Doug Pemberton

Umberto Pelizzari recently broke the world free diving record with a plunge to 131 metres off the coast of Sardine. Holding his breath for over four minutes, he plummeted into the abyss grasping a lead sled and once at maximum depth, posed for a quick picture before deploying a lift bag for a quick return to the surface. Holding his breath for that length of time is no great feat for Pelizzari, who has been timed holding his breath for over seven minutes and much longer after breathing oxygen. Those of us who like to spend a little more time on our dives than Umberto, so that we can relax and enjoy the experience, need more than just a lungful of air, so we stuff as much breathable gas into steel or aluminium tanks under pressures of 3000 psi or more. But breathing the gas directly at that pressure would leave a very nasty hole in the back of our heads and diving would quickly lose it's appeal. Therefore we need a regulator, the one critical piece of dive gear that allows us to leave our terrestrial world and venture into an aquatic environment for any great length of time.

Over the past 50 years a great deal of research, testing and experience has gone into regulator design and engineering. Basically all regulators do the same job, the two stages work together, through a series of springs, pistons, diaphragms and seals, to reduce the pressure of the gas in our tanks to a more manageable level for our lungs.

The first stage of the regulator takes the 3000 lbs and reduces it to an intermediate pressure (IP) of between 110 and 180 psi (IPs vary with each make of regulator).

This is still far too much pressure for our fragile lungs to handle so the second stage breaks it down to ambient pressure, allowing us to breathe normally. First stages are designed with either a piston or diaphragm and these may be either balanced or unbalanced, although unbalanced diaphragm regulators have pretty well disappeared. The biggest difference between a balanced and an unbalanced first stage concerns the air delivery to the second stage. In an unbalanced first stage, air delivery to the second stage is affected as tank pressure drops but in a balanced first stage, air delivery is unaffected by tank pressure and remains stable throughout the length of the dive. This is not to infer in any way that unbalanced regulators are inferior, both these types of regulators are very safe and when used within recreational limits, both will work well and the difference will hardly be noticed. But the differences are noticeable when those limits are exceeded such as in technical diving or when working hard underwater. Most of the "top end" regulators used in these disciplines are balanced and the general trend in regulator design seems to be heading towards balanced regulators.

Most regulator first stages come in a DIN and yoke version. DIN mounting allows a regulator to be screwed on to tanks containing higher pressures.

Regulators used to be big and klunky, made mostly of metal parts but over the past decade, tough, space age plastics and exotic metal alloys have made them smaller and much lighter, enhancing comfort and safety.

Many of the newer regulators are also bristling with features intended to decrease the effort of breathing such as a diver adjustable, breathing resistance control which can change the breathing effort on the second stage when greater or lesser air flow is needed. Another innovation is the venturi assist which reduces air flow resistance within the second stage.

For cold water diving, many regulators have special synthetic coatings on internal mechanisms to help discourage icing, while some first stages are environmentally sealed against the elements. All regulators come with soft silicone mouthpieces for comfort and other specialized and custom mouthpieces are available on the market.

Manufacturers are now designing regulators to meet the specialized demands of various divers. There are ultralight first stages and compact second stages for the weight-conscious dive traveller and regulators dedicated for use with nitrox and mixed gasses. Nitrox versions of regulators contain different O-rings and lubricants than other regs.

Over the years I've tried out most of the different regulators on the market and must say that there is no such thing as a bad regulator made by any of the major manufacturers. Technology and design have combined to develop a good, safe product but the differences are in the various features. When choosing a regulator we have to look and ask ourselves if, given the type of diving we do or plan to do, a particular feature is something we really need.

Another thing to look for in a regulator is the number of high and low pressure ports, make sure there are enough to accommodate all your hoses.

AQUALUNG - The U.S.Divers Micra ADJ is a tiny, low profile second stage with full breathing resistance adjustability. A diver-adjustable vane increases breathing performance for deeper dives. The SEA first stage is a compact, balanced diaphragm design with four low pressure and two high pressure ports. DIN adapters are available for most U.S.Divers regs.       SEA QUEST - Sea Quest's new XR2 second stage features diver adjustment of the inhalation effort and venturi control. The XR2 is also adaptable to be mounted so that it comes over either the right or left shoulder. The Spectrum is a balanced diaphragm first stage with four low pressure and two low pressure ports. Critical components are environmentally sealed and an optional environmental kit as well as a DIN connector are available.   SCUBAPRO - Mk 20 UL / G500 The Mk 20 UL is technically the same as the regular Mk 20 except that it is manufactured from marine grade aluminium, making it half the weight. It is a balanced, flow-through piston design with a thermal insulating system to combat icing. Two high pressure ports and five low pressure. The G500 second stage is 15% smaller than the G250 and a Delrin sleeve over the second stage chamber prevents freezing. A breathing resistance control knob and oversized venturi assist control switch are easily manipulated. Will be available in early summer.   SHERWOOD - The Sherwood Oasis is a very small, lightweight second stage with an extended exhaust tee to keep bubbles out of the line of sight. Two small fins within the second stage are designed to collect condensation from exhaled breath and return it to combat the possibility of dry mouth. The B5705 is a balanced first stage with two high pressure ports and five low pressure ports. Nitrox conversion kits are available for all Sherwood regulators.   TUSA - New for 1997 is the TR 390 IMPREX AD2, an in-line, balanced piston first stage with two HP ports and four LP ports. It weighs in at just 21.5 oz and has a heavy duty 4000 psi yoke. The second stage has a breathing resistance control and an internal air deflector for easier breathing.       OCEANIC - The Oceanic Gamma is a compact, second stage, with an oversized purge button for easier manipulation. It also comes in a Nitrox version. Both balanced diaphragm and balanced piston first stages are available and incorporate two high pressure and four low pressure ports. The balanced diaphragm DX3 is also available with DIN.       ZEAGLE - The Zeagle Tech is a pneumatically balanced second stage. A diver adjustable, easy-to-grab, venturi assist lever and breathing resistance knob make for easy fine tuning. The 50D first stage is an environmentally sealed, balanced diaphragm design with four low pressure and two high pressure ports. All regulators are available in DIN or yoke and Zeagle also offers an optional DIN to yoke converter.     DACOR - The Dacor Pacer XP is a rugged, lightweight, mechanically balanced, non-adjustable second stage. Internal components are Teflon coated to resist icing. Pacer Ice first stage is a balanced diaphragm design and is environmentally sealed against extreme cold. Two high pressure ports and four low pressure ports, two of which are 1/2 inch and the other two being 3/8". All Dacor regulators are available in DIN or yoke configuration.

DIVER would like to thank Oceaner, Dive and Sea and Aqua Sapiens for their help in preparing this article.