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March 2007 Vol. 22, No. 3   RSS Feed for Undercurrent Issues
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You've Come a Long Way, Nitrox

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from the March, 2007 issue of Undercurrent   Subscribe Now

Anyone certified in the past ten years might presume that Nitrox has been a favorite of sport divers forever. Not so. Nitrox has been available to sport divers for 22 years, but politics and controversy about its use raged through the dive industry for nearly half that time.

Nitrox was introduced to recreational divers in 1985 by Dick Rutkowski, a NOAA Deputy Diving Officer, but it took more than a decade for the entire dive industry to embrace it. DEMA, PADI, Skin Diver magazine and many dive operators were against it well into the 1990s. They argued that Nitrox was patently unsafe and led to deeper, more risky diving. They believed that Nitrox was rashly being promoted by businesses just wanting to make money from Nitrox training and equipment sales. The Diving Equipment and Marketing Association went so far as to prevent any mention of Nitrox at their annual conventions. The Cayman Dive Operators Association said they wouldn’t treat Nitrox-using divers who got the bends. Undercurrent editorialized frequently about the foolishness of these arguments.

They wouldn’t treat Nitrox
divers who got the bends

The major defenders included NAUI and NASDS, arguing that the safety record of Nitrox was nearly perfect and that opposers were just trying to protect their own turf. Regardless of the controversy, divers took to it like water—234,000 divers became Nitrox-certified between 1987 and 2000. A major milestone occurred in 1996, when PADI finally accepted Nitrox. Now the gas can be found in nearly every dive school, shop and liveaboard, and the word “Nitrox” is displayed at hundreds of booths at DEMA’s annual show.

Better than compressed air?

Nitrox, of course, allows greater bottom times for no-stop dives and shorter stops during decompression dives than compressed air. Over the years, researchers have studied Nitrox’s effect on divers’ fatigue, gas consumption, decompression stress and other symptoms. While divers make all sorts of claims for Nitrox, so far researchers have found no significant differences between Nitrox and compressed air. A study published in Undersea Hyperbaric Medicine in 2003 tested 11 divers breathing either Nitrox or compressed air for 40-minute bottom times at 55 feet. Divers were assessed before and after their dives, and no group measured differently in fatigue, attention levels or ability to concentrate.

A DAN workshop in 2000 focusing on Nitrox found no evidence that Nitrox increased the risk for decompression sickness. It also found no evidence of an unreasonable risk of fire or ignition for divers with standard dive equipment using up to 40 percent Nitrox. Last year, Michael Lang, director of the Smithsonian Scientific Diving Program, took a look at DAN data on mixed-gas diving fatalities and injuries since the 1990s. In an article for Diving and Hyperbaric Medicine last summer, he published his findings:

• A higher proportion of safe divers used Nitrox than of divers who were injured on dives
• Nitrox divers were typically older than air divers, and 60 percent of them had specialty training
• Safe Nitrox diving was most common aboard charter boats, and there were no air or Nitrox fatalities from liveaboards
• Nitrox divers dived deeper than air divers, but they did fewer dives over more days
• Injured divers and diving fatalities had higher proportions of rapid ascent and running out of gas, but the use of Nitrox or air was not a significant facto

He also found that in the past six years, the certification numbers of Nitrox instructors and divers has approximately doubled, but there is no comparative increase of DCS rates in Nitrox divers. One million more Nitrox dives were done in the last six years than in its entire history of use. Liveaboards report that most of their divers are exclusively Nitrox users, but Lang says the fact that they are not reporting higher DCS rates shows the gas isn’t causing any more safety hazards than air does.

“There’re really two things to be cognizant of as a Nitrox diver—the amount of oxygen in your Nitrox mix and your maximum depth,” Lang told Undercurrent. “There’s no higher risk of narcosis or fatigue. You wouldn’t even know you were breathing Nitrox unless you saw the mark on your tank. You don’t even need to be an experienced diver anymore; dive schools will teach novices how to breathe Nitrox from day one.”

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