SAFETY Diving Enriched Air (Nitrox) with Your Dive Computer Set to “Air” – by Dan Orr, President, Dan Orr Consulting
Enriched Air Nitrox (EANx), com- monly referred to simply as “nitrox,” once scorned by segments of the div- ing industry and referred to as “voodoo gas,” has truly revolutionized recreational diving over the last several
director, developed the first nitrox training program for recreational divers in 1985. As a side note, I had the privi- lege of being in the first course where Dick Rutkowski cer- tified nitrox instructors, with my nitrox instructor number being 10). The key benefits of nitrox as a breathing gas are: Longer allowable bottom times at given depths (com- ▪ pared to air) Shorter required surface intervals ▪ Reduced post-dive fatigue (anecdotally reported by ▪ divers) The risks specific to nitrox as a breathing gas are: Increased risk of oxygen toxicity, particularly at ▪ higher partial pressures of oxygen (PPO2) The need for careful monitoring to avoid exceeding ▪ maximum operating depth (MOD) Requirement for specific training and situational ▪ awareness Dive computers are designed to automatically calculate
decades. By increasing the percentage of oxygen and re- ducing the percentage of nitrogen in breathing gas, nitrox allows divers to enjoy longer bottom times and reduced de- compression stress – provided it is correctly and thought- fully used. One crucial aspect of nitrox diving is proper dive computer management, as dive computers are our pri- mary tool for tracking exposure to both nitrogen and oxy- gen. A common question among divers, particularly those new to the use of nitrox as a breathing gas, is whether it is safe or acceptable to dive with nitrox while leaving your dive computer set on the “Air” setting. Nitrox is a breathing gas mixture with an oxygen concen- tration greater than 21% (the amount in surface air) and a correspondingly lower nitrogen percentage than 78%. The most common recreational nitrox mixtures are either
EANx32 (Enriched Air Ni- trox 32% oxygen/68% ni- trogen) and EANx36 (Enriched Air Nitrox 36% oxygen/64% nitrogen). The reduction in nitrogen is what gives nitrox its pri- mary advantage: by breath- ing less nitrogen, divers’ tissues absorb less nitrogen
and display your remaining no-decompression time, ascent profile, and other critical information based on the gas you are breath- ing. As mentioned in a pre- vious article (Safety Stops – September 2025), dive computer algorithms, while designed to reduce
during a dive, which extends no-decompression limits (NDLs) and reduces the risk of decompression sickness (DCS). While no single person can be credited with "inventing" nitrox as a concept, as various individuals and entities have contributed to its development and use in diving over time, J. Morgan Wells, former director of the National Oceanic and Atmospheric Administration's (NOAA) Diving Pro- gram, is recognized for developing and standardizing pro- cedures for diving with oxygen-enriched air in the late 1970s. Wells also proposed standardized breathing gas mix- tures for use by NOAA. (Note: It's also worth noting that Dick Rutkowski, retired NOAA diving program training
the likelihood of DCS, are based on theoretical models and therefore do have limitations. They are designed to calcu- late safe dive limits by factoring in a variety of real-time measurements, but the effectiveness of these algorithms can vary. Divers should understand these limitations and consider - and communicate this to their diving compan- ions - their personal risk factors when diving, especially when using breathing gases other than air. When set to “Air,” the computer assumes you are breath- ing the equivalent of surface air (21% oxygen, 79% nitro- gen). When set to a nitrox mode, you input the appropriate oxygen percentage for the breathing gas you are using, and
PAGE TEN | SCUBA DIVING INDUSTRY
Made with FlippingBook - Online Brochure Maker