Monday, April 29, 2013

Rebreather opens up a whole new level of scuba diving

Like many divers, Mike Lynch anticipated his venture into the great blue beyond following his open water certification would be peaceful, serene and quiet.
Well, two outta three ain’t bad.
While scuba diving is peaceful and serene, it’s not always quiet, thanks to the never-ending pulse of expelled breaths and the resulting bubbles escaping past the diver’s ear. Breathing air in from a pressurized tank and expelling used air into the water column has always been a part of diving in general and scuba diving in particular.
But for serious divers, and those with both the skills and the disposable income, rebreathers offer a panacea of underwater enjoyment.
In the past year, Lynch, a diving friend of mine who works with Bruno’s Dive Shop in Clinton Township and Titan Dive Group, became a certified rebreather diver, and the stories he has to tell are amazing. Four-hour cave dives with an average depth of 120 feet and such quiet tranquility that he can hear the water moving around in the cave system and rocks cracking on each other as they roll around in moving water. Fish swimming right up to his mask to see their reflection because they aren’t scared away by expelled bubbles.
“It brings you into a whole new world of diving,” Lynch said.
Lynch, repping Titan at the Great Lakes Shipwreck Festival in March, gave me an up-close and personal explanation of how the rebreather works.
In the most basic terms, the rebreather uses two tanks, one containing pure oxygen, and the other containing regular air used as “filler.” Each tank is smaller than a traditional scuba tank. With each breath, the used air is recirculated using a scrubber to remove the carbon dioxide, and additional oxygen is added to the “filler” air. The system is constantly evaluating the user’s gas needs based not only upon their own metabolic rate, but also things like the dive depth. According to Lynch, it creates a perfect nitrox mix for the entire dive.
It is a much, much more efficient way to use gas, since it is all recycled and reused. A typical “open circuit” scuba unit, with expelled bubbles, wastes a significant amount of oxygen. In a typical breath, only about 4-5 percent of the oxygen is used, and the rest is expelled into the water. With a rebreather, that unused oxygen is pushed back in the system and mixed with the filler air and oxygen. Lynch said that during his four-hour cave dive at an average of 120 feet, he only used eight cubic feet of oxygen.
While the idea and the concept of rebreathers have been around for more than 200 years, mass-produced recreational rebreathers have only been around for a little more than 20 years. The last 10-15 years have seen significant technological advancement.
Nevertheless, cost remains an issue. Lynch said a diver looking to get into rebreather technology can expect to spend about $10,000 for the equipment, the training and the gas to get started.
In the video above is my interview with Mike Lynch and our discussion about rebreathers.


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