The use of nitrox in everyday recreational diving is skyrocketing. Just look through the pages of SKIN DIVER for the previous six to eight months. You will see live-aboard after live-aboard and dive shop after dive shop advertising nitrox availability. There is a good reason for this. If used correctly and safely, nitrox can increase your bottom time when compared to normal air. It reduces the introduction of nitrogen to your system, allowing you to make longer multiple dives, as you would on a live-aboard or a dive holiday. When used with air tables, nitrox may reduce your chances of getting bent. But, there is a definite bottom limit to every nitrox mixture, a hard deck as it were. Going below this limit can result in oxygen toxicity, even with only a 10 foot margin of error. To help you better understand the complexities and benefits of this type of diving, SSI (Scuba Schools International) now offers a simple to understand, yet comprehensive recreational nitrox certification specialty course.
Using nitrox requires special training, preparation and pre-dive planning. The first element of the SSI course is the manual. The easy to read text covers each component step by step and reinforces each lesson with review questions at the end of each chapter. The first chapter gives an overview of nitrox, its misperceptions, benefits and limitations. Chapter two delves into the physics and physiology of diving on nitrox, including depth limitations, oxygen toxicity and the concept of partial pressure of oxygen as the determining factor of nitrox depth and time limitations. Chapter three presents an overview of equipment considerations for diving with enriched air. This includes cylinder markings and the need to analyze every tank of nitrox before you dive with it. Unlike regular airfills, nitrox mixtures vary, requiring divers to personally check the oxygen content of each and every tank. The manual covers the use of the specialized tools for this task and the safety procedures required of both the dive shop and the diver.
The essence of nitrox is the ratio of oxygen to nitrogen. The two most popular mixtures are EAN 32 (32 percent oxygen) and EAN 36 (36 percent oxygen), also known as nitrox I and nitrox II. (The air we breathe contains approximately 21 percent oxygen.) But, nitrox fills can vary from between 22 and 40 percent oxygen and each percentage level has specific time and depth limits. A specialized set of dive tables is included with the SSI course; their use is similar to that of regular tables.
Chapter four goes over the real skill of nitrox diving: use of these special nitrox tables in preparation for the dive. Here, comprehensive instructions in the use of the Equivalent Depth/CNS 'Clock' Exposure Time Table and the Combined Air/ EANx dive tables are given. There are some detailed specifics that are too much for the scope of this review but the manual explains each step clearly and concisely and, with a little practice, their use should become second nature.Diving on nitrox has many benefits. But, just as in life, with privilege comes added responsibility. I would suggest nitrox training for divers with better than average basic skills, including excellent buoyancy control, and a good many dives logged under a variety of conditions. The SSI Enriched Air Nitrox course manual and tables (along with the classroom and open water instruction) offer complete and thorough training in this very worthwhile and advantageous specialty skill.
For more information on an SSI training facility near you, contact SSI at 2619 Canton Court, Fort Collins, Colorado 80525-4498; (970) 482-0883, fax (970) 482-6157 or visit the Web site at http://www.ssiusa.com.