Beyond the Basics

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Rick Murchison

Trusty Shellback
ScubaBoard Supporter
Scuba Instructor
Messages
13,348
Reaction score
561
Location
Gulf of Mexico
# of dives
2500 - 4999
The following article was written as an introduction to an Advanced Nitrox course a few years ago, but it's a pretty good introduction into this "grey area" between recreational and technical diving... some food for thought :)
Rick
--
Beyond the Basics – Safely Handling Increased Risk
© 2002 G.R. Murchison CDR USN(Ret)

Advanced Nitrox and Deep Nitrox diving expand the envelope of our diving adventure into new areas, closer to the edges of the human diving experience. In the basic Nitrox course we introduced the concept of increased risk along with increased safety. We introduced the fundamentals of realizing the substantial benefits of Nitrox diving while keeping risk of the increased exposure to oxygen at an acceptably low level. As we expand our diving envelope to take more advantage of our continued training, greater experience, better skills and improved/additional equipment, we also need to realize that risk increases too, and therefore we must expand on that basic risk management philosophy we introduced in the Nitrox Diver course.

The Safe Diving mindset

The Safe Advanced Nitrox Diver recognizes and accepts that there is increased risk in diving “Best Mixes” and in decompression diving, and takes positive proactive steps to ameliorate that risk. This course itself is the first step in defining, recognizing, accepting and handling those risks in a positive, safe manner. Increased attention to detail in every aspect of each dive from site selection to dive objectives to specific equipment configuration to detailed gas planning and management, as well as preparation for and competence in handling any emergency situation that might arise are hallmarks of the safe Advanced Nitrox Diver. The Advanced Nitrox diver does not cut corners.

Redundancy principles

One specific way to reduce risk is through redundancy. Where any equipment failure could cause injury or death, a backup is required. By having a second completely independent gas supply, for example, the Advanced Nitrox Diver is prepared for a gas supply failure. We will examine each piece of gear we need for our dive, and if the loss or malfunction of that piece of gear would cause a danger, we will carry a second one.

Eliminating Failure Points

Almost any piece of equipment can fail. For example, the chance of any given light bulb failing when it is turned on may be one in a thousand. If we have two light bulbs and we turn them on then the chance of having at least one of them fail would be two in a thousand. Adding light bulbs would increase the chance of having at least one of them fail, until, by the time we have a thousand light bulbs, there would be a near certainty that at least one of them would fail whenever we turned them all on, and on average we’d have one failure every time we turned them on. If our criteria for aborting a mission included a light bulb failure, then having a thousand of them would all but assure we could never go on a mission. But we’d have plenty of light when we didn’t go! Our goal in eliminating failure points is to look at each piece of equipment carefully to determine if we really need to have that piece of equipment and if not, we don’t carry it.


Putting Redundancy and Failure Point Elimination together

We will carefully consider each component in our dive equipment to balance redundancy and failure point elimination, with the goal of maximizing safety and enjoyment of our dives. Let’s look at regulators as an example. Obviously, we need a reliable gas supply for a safe dive, and if any regulator fails it is grounds for aborting the dive. As Open Water Divers, if we experience a free-flowing regulator we can simply initiate a controlled ascent to the surface. We may have to abort the dive but we are not at risk of any serious injury if we follow standard procedure and ascend at a controlled rate, or share air with a buddy so we can even include the extra margin of a safety stop. If we are on a dive requiring a decompression stop, however, that controlled ascent all the way to the surface may indeed result in serious injury, so it isn’t a safe option. We need to be able to assure the ability to perform our decompression stop with or without our buddy; and we need the gas to do it. Since the standard recreational diving Air Delivery System has no way of preventing a free flowing regulator from depleting our entire gas supply, we must modify the system to provide redundancy. The Advanced Nitrox Diver will therefore have two independent regulators, either attached to independent gas supplies, or with the ability to shut down the free-flowing regulator and make all the remaining gas available to the other regulator. A third regulator is not carried (unless a different decompression gas is used – which will be discussed later) because it adds another failure point without changing our ability to safely complete the dive.

Mature Diving Objectives

Advanced Nitrox Divers are not trying to set any records for depth or time or distance. Our goals are a more extensive use of the equipment available to us in a safe, enjoyable environment. And while we are expanding our diving limits in this course, we are not “pushing” them. We will do the requisite planning and carefully consider all aspects of each dive to assure a safe, enjoyable experience. We will learn that thorough planning of all aspects of a dive reduces stress, increases safety and greatly enhances diving fun.

The Overhead Environment

In our Open Water diving up to this point, we have always reserved the escape to the surface as the ultimate safety valve, the final option. Now we are going to make the conscious decision to go beyond that, and impose a “ceiling” that is still under water between us and the surface. Not a physical ceiling yet, but a physiological one that is just as real in terms of our safety. Much of what we do in this course is learning how to safely cope with that ceiling.
The Staged Decompression Stop is a required delay at a specified depth for a specified time to allow off-gassing to occur sufficiently to safely continue an ascent to the surface.
Reduced “escape” options: Unlike a “safety stop,” whose intent is to drive our chances of decompression sickness from tiny to infinitesimal, the staged decompression stop is required to keep the risk of decompression sickness at an acceptably low level. And since it is required, it becomes a temporary ceiling. While it exists we must retain the ability to safely remain below it.
The need to plan: This requirement to remain below a ceiling means that our entire approach to each dive must take on a new level of planning, control and equipment reliability, for we can no longer “just abort” the dive and head for the surface. We will find new meaning and significance in such things as Surface Consumption Rate, Boyle’s law, turn pressures, times, depths, buoyancy control, instrument monitoring and the like.

Summary

Along with the expanded diving envelope we gain as Advanced Nitrox divers, we also incur additional risk. To safely and fully enjoy that expanded diving envelope, we must take positive steps in planning and executing our dives to ameliorate that increased risk, including redundant equipment, the elimination of failure points, setting mature diving objectives and being prepared for emergencies. We don’t consider Advanced Nitrox to be a “technical” diving course, but we will introduce many of the principles, concepts and practices that separate the “technical” from the “recreational” diver. As an Advanced Nitrox Diver you will be a truly advanced recreational diver, and you will be equipped with the skills and knowledge to make the “Tech” decision when you are ready and if you desire to do so.
 
nice one, unkie rick! thanks a bunch for sharing.
 
As I am currently pursuing this path, this is an excellent read. I am in the middle of an Adv. Nitrox course. While it does have some challenges for me, I have been chipping away at these challenges bit by bit. Hope to learn different perspectives & views.
 
very usefull article, i'm working twards this path and this is good information, thanks rick
 
I'm still having trouble finding time for my Intro to Nitrox, but I'm working in this direction as quickly as possible - thanks for the read!
 
This may be a silly question, but what organization provides the Advanced Nitrox Course? I've been diving for a year, consistently 2-3 trips a month this season, and recognize everytime I go how much I have to learn. As much as I read and pick-up from this forum, I prefer formal classes for the introduction and application of new material. But hey, all you guys who've been diving for years, keep talking so I can keep reading!!
 
... what organization provides the Advanced Nitrox Course? ...
SSI (TechXR), IANTD, TDI, NAUI Tech, ANDI, others...
Rick
 
Good post Rick. I would add that once you get to and through the Advanced Nitrox course/stage of diving that the skills learned should be practiced by the diver as a matter of routine. I am probably stating the obvious, at least to members of this board (we are all fanatics), however the constant repetition of skills is, I think, paramount to being able to rely on them in a real emergency.

I am sure course structure is different by agency. IANTD uses Advanced Nitrox also as an introduction into tech diving, including, gas management, equipment configuration and redundancy, shooting lift bags, drop and retrieve of stage cylinders, valve shutdowns, introduction to deco, air sharing on long hose configurations, etc. Going forward to Trimix, full tech is incorporated with all the above skills, but also more comprehensive gas management, full deco training, managing bouyancy failures, more equipment failures (such as a QD failure if you have one on your harness), operating in zero visability environments...etc. etc.

I am sure all the agencies offer these and additional skills during the course of training, but I think it is incumbant that the diver take the time to practice to retain and perfect the skills.
 

Back
Top Bottom