"Bat gas" allows the deep dive | TahoeDailyTribune.com

"Bat gas" allows the deep dive

Gregory Crofton, Tahoe Daily Tribune

“Bat gas,” or the right mixture of helium, oxygen and nitrogen, allows divers to reach the inhuman depths of the S.S. Tahoe.

Brian Morris, a 38-year-old attorney in Reno and avid diver, is the brains behind the operation. New Millennium Dive Expeditions uses his software, Departure, to map out ascent and descent shedules on their daring dives.

Gas bubbling in a human bloodstream is what causes the bends, a condition that occurs when someone doesn’t allow adequate time for a body to decompress gas it has taken in.

Morris said his method allows more time for the body to deal with the gases and decreases the chance for bubbling.

“You do stops (in the water) deeper,” Morris said. “By doing them deeper, more pressure on the body helps minimize or keeps you from bubbling and the gas building up comes out faster.”

Submerged 20 feet, the divers breathe pure oxygen from a line fed from their boat. There, they check equipment and make sure everything, including five tanks, two under an arm and three on their backs, are in order.

During their quick descent, they breathe a mixture that’s 11 percent oxygen, 63 percent helium and the rest nitrogen.

Floating to the surface, they tap into a tank at 190 feet that’s 21 percent oxygen, 25 percent helium and nitrogen. Sixty feet higher, they breathe a mixture that’s 30 percent oxygen until they rise 20 feet of the surface and again breathe pure oxygen fed to them from the boat.

The team breathes more helium and less oxygen the deeper they dive because oxygen becomes toxic under pressure, Morris said. These days, technical divers opt to use helium instead of more nitrogen because nitrogen can disorient someone if they breathe too much of it.

Humans who aren’t under water breathe 21 percent oxygen and 79 percent nitrogen.

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