Out of air with half-full tanks (http://cavediverharry.com/isolator/)

An article in a recent edition of DAN’s Alert Diver magazine warns of the perils of diving with an isolator valve you only think is open (link below). While your SPG may be telling you that you have phenomenal gas consumption, the reality is that you are sucking the right side of your doubles dry and may soon run out of air without warning. This story hit close to home for me, as I’ve witnessed this same situation twice…and experienced it once.

Each of these three situations had different root causes, and each teaches one or more lessons in its own right. Let’s take a look at each situation and what you can learn from it.

Open a partial turn?

This story goes back nearly 20 years, to what my friends call Harry’s Hogarthian Phase (i.e., the days before sidemount). Some of my fellow cave instructors were espousing an approach to diving manifolded doubles in which you opened your isolation valve just a partial turn. The idea was that, should something start to leak badly, you could isolate almost instantly and, thus, safe half your remaining air. This seemed logical to me, so I started doing it.

Everything worked fine until the Dive Rite gang and I made our first trip aboard Rick Pitts’ Ultimate Getaway. We were diving a wreck at 130 feet. I was using a set of manifolded steel 72s I’d put together just for this trip (a sweet setup if you do not need a lot of gas).

When diving manifolded doubles in caves, I’ve always made a practice of starting each dive by reaching back and confirming the position of all three valves while standing in chest-deep water. At sea, this wasn’t an option, so I did it while standing on a rocking boat deck.

Five minutes into the dive, I was marveling at my exceptional gas consumption. My SPG showed that I’d only used a couple of hundred pounds (actually a result of the tanks cooling).

Ten minutes into the dive, with my SPG not having moved past this, I decided Something Was Wrong and called the dive. In retrospect, what I was seeing should have been a clear warning of a closed isolator, and my response should have been to double check the position of all three valve turnwheels. However, being as I was a conscientious diver and had checked this prior to the dive, I assumed it had to be something else, like a faulty SPG.

Upon surfacing, I noticed that the first stage on my right post was moving rather freely. Out of curiosity, I tried detaching it from the tanks without first shutting down the valve. It came right off in my hand. This meant that, while I was fighting rough seas trying to get back on the boat, I was mere seconds from running out of gas (whoops!).

So what had happened? Apparently, prior to the dive, the boat lurched while I was checking the position of the isolator valve. As a result, I inadvertently closed the valve while thinking it was still open a partial turn.

Lessons learned: There are actually three:

·         To start, your isolator is like your other two valve turnwheels; it should be all the way open or all the way closed. In fact, except in an emergency, it should never be anything but all the way open. Yes, if need be, it will take a little longer to isolate — but it won’t put you at risk of being suddenly without air. A partially open isolator is too easily closed by accident.

·         Second, beware suspiciously good gas consumption. No, your breathing rate didn’t improve miraculously. Gas consumption that’s too good to be true actually means something isn’t right.

·         Finally, check your turnwheels. It should be the first thing you do if you don’t appear to be using any gas. Yes, we know you checked them at the surface; check them again. You may be surprised at what you find. And you may be able to save your life, if not the dive.

 

 

Make sure you fully understand your manifold before using it

These days, most cave instructors want students to have prior experience in backmounted doubles before using them in a course. This wasn’t always the case. Before tech diver training became widely available, a Cave Diver course often provided a student’s first introduction to doubles.

This was the case some years ago when I had a student in his second day of training on doubles. Prior to the first dive of the day, I had the student reach back and check all three valves, to confirm they were all the way on. He did — although his head blocked my view of exactly what he was doing when checking his isolator valve.

While exiting, the student suddenly flashed his light and gave me the out of air signal. I responded by immediately passing a second stage and switching to the other. I then reached back and checked his manifold, starting with the isolator.

You guessed it. It was fully shut, and he’d sucked one half of his doubles dry. Have you ever heard the noise a set of doubles makes when you open the isolator and equalize the pressure between tanks? It’s one you won’t forget.

So what happened? Two things:

·         Despite my having spent considerable time on manifold function and operation, the student failed to grasp the part about never shutting your isolator, except in an emergency. So, as the end of the previous day, the student dutifully shut down his outboard valve turnwheels…then did the same with the isolator. He then proceeded to attach the fill whip to the left post, leaving the entire right side of the doubles close ro empty.

·         When checking his valve turnwheels prior to the next dive, the student only check to see that the isolator turnwheel was fully turned in a direction…just not the right direction. Had he turned the valve in the opposite direction before checking to make sure it was turned all the way in one direction or the other, he would have heard the sound of gas moving rapidly through the manifold. I would have seen this, except for the fact his head was in the way.

Not only had this never happened to one of my students before, I’d never heard of it happening to anyone else’s. I’d tell you that I always made a point of checking this with students from this point one, but the fact is, after this student, I never had another student who wanted to learn in anything but sidemount.

Lessons learned: Four things here:

·         Leave the isolator valve all the way open, all the time (except, of course, in an emergency).

·         When filling doubles, check to make sure that both sides are being filled.

·         When checking turnwheel position prior to a dive, back off slightly on each valve before turning it all the way in the right direction.

·         And, finally, practice manipulating your manifold turnwheels until you are totally clear on which direction is clockwise (off) and counter- or anti-clockwise (on).

Complacency kills

It’s not easy admitting that you’ve screwed up or, worse, allowed a student to screw up. I can, however, take solace in the fact I’m not alone.

This story took place in 2000. It involves a regular dive buddy, Gareth, and another friend whom I’ll save embarrassment and simply refer to as “Herschel.” Herschel is a vastly more knowledgable and experienced cave diving educator than I am — and there are not a lot of people who can say that. Nevertheless, even the best among us can have a bad day.

On this particular day, Herschel had invited Gareth and me to accompany him on a dive in a system that, even now, not many people have seen. We were nearly 2,000 feet back, enjoying what, for us, was an entirely new cave, when we hear a voice behind us go, “Thit! Thummavabith!” We then heard the distinctive sound of gas rapidly rushing from one side of a set of doubles to the other, followed by a flashing of light and a thumbs-up signal, calling the dive early.

So what happened? It seems Herschel had made the same mistake my student had just a few years earlier; he’d filled his doubles with the isolator closed. And, in this case, he couldn’t claim that I hadn’t taught him about that.

Lessons learned: No one is bulletproof. Everyone makes mistakes. They say that, for the first 50 dives, most new cave divers are filled with trepidation, given the graphic images of death and destruction with which their instructors have filled their imaginations. Then, having survived their first 50 or more dives, they start to get complacent. They cut corners. They stop believing it can happen to them. This is when the most fatalities occur.

A friend once said that, if you are very lucky, you will get to make one big mistake…and survive. Whether or not you continue to survive depends on whether you learn from the experience or blow it off. Who knows? You might get lucky. But you probably won’t.

So what have we learned?

Perhaps we can best sum it up this way:

·         Isolators are like any other valve. Other than in an emergency, they need to be turned all the way on.

·         Don’t fill your doubles until you first check to make sure the isolator is turned all the way on.

·         Check to make sure all three turnwheels are all the way on at the start of the dive — but don’t assume that guarantees anything.

·         No, your gas consumption will not improve dramatically over the course of just one dive. If your SPG fails to drop more than just a couple hundred pounds within the first ten minutes, stop and check valve position. Fix any problems you find and call the dive if necessary.

·         You are not bulletproof — no matter how much experience you have. Never forget the cave is trying its damnest to kill you dead. Don’t let complacency help it along.

Diver’s air consumption appeared unbelievably good!

Diver’s air consumption appeared unbelievably good!

Buddies share air on ascent when one of them mistakenly thought he was running out of air.

REPORTED STORY:

The day started out as usual for a diving day; my buddy and I assembled our gear and everything went as normal. I dive with double 12 liter (~95 cu ft) tanks with a back plate. We used drysuits since this is cold water diving and we planned the first dive to a wreck at a maximum depth of 30 msw (98 fsw). Since my air supply is almost double that of my buddy, I tend not to check too often. I check my submersible pressure gauge (SPG) just once in a while as I know my buddy will run out of air much sooner than I would anyway. When I eventually checked my SPG it had just moved slightly (about 20-30 bars, ~300-400 psi). I thought this was very strange, but I knew my air consumption was starting to become quite good lately. Still, I thought this was way too little air consumed. At the safety stop, I tapped my SPG just to see if anything happened, but no, it still showed around 180 bars (~2600 psi) left.

When we came up, we started discussing this and we both wondered what could cause this extremely low consumption. We also put on my buddy's regulator and SPG just to see if the pressure was same, and it was. I thought that maybe since a guy at my club had filled my tanks, he may have accidentally put 300 bars (4350 psi) in my tanks and that I was a bit sloppy when I read the gauge before entering the water. I could remember that it was just above the major marker and I asked myself, was it just above 200 bars or 300 bars (3000 or 4000 psi)? To me this might explain such apparently low consumption.

We completed our surface interval and kitted up again; the pressure in my tank was 180 bars (2600 psi) and that was more than enough for a second dive. We planned the second dive to a max depth of 18 msw (59 fsw). An open water diver asked to join us which was, of course, no problem. The plan was that I would stay in front as I wanted to do some photography, the new diver would stay in the middle, and my buddy who is an instructor would stay in the back. The dive was uneventful for about 25 minutes when suddenly, I felt resistance when I was breathing.

I asked myself, "What is happening now?" Almost at that same time, I was suddenly unable to take a breath. Quickly, I turned around to find my buddy who was just 1-2 meters (3-6 feet) behind me. I gave the out-of-air signal and he grabbed for his octopus. It felt like forever, but the time from when I gave the signal to when I got my first breath from his backup could not have been long. For the first few breaths, it felt like his 1st stage did not deliver enough air; but when I managed to calm down more, breathing became easier. Even though I think we both reacted calmly and did not panic, I felt stressed until I was sure I could get air from my buddy's backup.

We signaled to the third diver that we would start the ascent to the safety stop. We did that and on the way I was starting to think about my backup around my neck. I purged it and there was still air coming from that. So at the safety stop, I switched to my backup and let go my buddy's octopus. We finished the safety stop and ended the dive.

At the surface, we started talking about what happened. My buddy thought, at first, that I was just "testing" him because I started using my backup in the safety stop. But when we started to look at my gear we found out what was wrong.

The isolator valve on the manifold was closed so I breathed the tank on my right side till it was empty and the amount of air that was used on my SPG was just the air I had inflated my drysuit with from the tank on my left side.

When I thought about it later, all the signs should have been enough to understand what was happening, but we still overlooked the real issue. Thanks to our practice of staying close together when we do cold water diving where the visibility is sometimes very poor, my buddy was not far away this time to help me out. We have talked about it several times after and we think we reacted in a good way when the situation became real. It shows that if you keep calm and don't panic then it is much easier to solve the problem you are presented with. The open water diver told us when we came up, he thought it was just a drill and not a real incident. What I have learned though is to always check everything and don't assume that things are as you left it.

COMMENT:

No-one expects to run out of gas but sadly, every year a number of divers panic when it happens unexpectedly even if their buddy is nearby. This diver signaled his buddy and secured an alternate air source before commencing his ascent. Later, he realized the cause of his apparent ‘out-of-gas' incident. No doubt when he opened his isolator valve a fraction then he would have heard the air moving from his left tank into his right tank until they were at equal pressure.

This is not an uncommon problem with isolator valves in manifolded doubles and a common method to prevent this problem is to perform shut-down drills before descending. Known as S-drills, this is where each diver reaches behind the head to shut down then fully re-open each valve. In this particular case it appears the divers did not check all their valves and inflating the drysuit, (plus possibly cooling of the tanks), caused the pressure in the left tank to fall slightly during the dives, further masking the problem.

When wearing a set of manifolded doubles, divers might remember this advice: if your air consumption appears too good to be true, then check your isolator valve because it probably is.

~ Peter Buzzacott, MPH, PhD

Overweight divers put themselves and others at risk

By Patrick Roward

It’s been one year since your last vacation. You’ve worked hard and now you can’t wait to arrive in Key West and dive the USS Vandenberg. You’re on the dive boat heading out for the dive when you’re asked to buddy up with a guy who is 5 feet 10 inches tall and weighs 250 pounds. You think to yourself, If something goes wrong and this guy goes into cardiac arrest at depth, will I be physically able to help him? Or worse: If something goes wrong with my dive, will this person be physically able to help me?

Obesity is defined as an excessive amount of body fat greater than 25 percent in men and 35 percent in women. Another measurement to determine body composition is called a Body Mass Index, or BMI. A BMI is used to assess weight relative to height, and can help determine whether an individual is obese, overweight or underweight.

A DAN study, “Classification of DAN Recreational Diver Fatalities by BMI from 2002, 2003 and 2004,” showed that at its worst, divers with a BMI of 30 or greater — which is considered obese — made up 53 percent of the dive-related deaths, whereas divers with a normal or healthy BMI of 18.5 to 24.9 made up only 13 percent of these deaths. Still, the issue isn’t just about being obese, but the health-related problems that obesity can cause and how these health issues can affect divers. It has been documented that obesity places a person at a significantly increased risk for hypertension (high blood pressure), Type II diabetes, excess levels of serum cholesterol, stroke and cardiovascular disease.

“Prudent dieting and regular exercise should go hand-in-hand for divers,” according to a 1999 DAN report, “Cardiovascular Fitness and Diving.” “Older individuals who take part in recreational diving and have a family history of heart attack, especially at an early age, should receive appropriate evaluations to detect early signs of coronary artery disease.” In DAN’s “Diabetes and Diving — Update 2005,” it’s written that “individuals with Type II diabetes have generally been excluded from scuba diving because a possible loss of consciousness might pose a significant risk, affecting the diver’s ability to take care of himself/herself or his/her dive partner.”

What does all of this tell us? It tells us that, normally, scuba diving is a fun and relaxing activity, but that on occasion catastrophic events can and do take place. When these events happen, every diver should be able to take care of himself and his dive partner.

I believe it’s the responsibility of every diver to keep as healthy as possible. By allowing yourself to gain excess body fat and fall into poor health, you’re not only placing yourself in danger, but also your dive buddy and every diver who chooses to come to your aid if a problem should occur. If you choose to let your weight get out of control, then you also have to decide whether a day in the water is really worth your life or the life of other divers.

An exercise physiologist, Patrick Roward has more than 20 years working in the field of health and fitness, with the majority of his experience in cardiac rehabilitation, strength and conditioning of athletes, and health promotion.

It’s not a matter of weight, it’s a matter of fitness

By Marc Weiss

**** I love to scuba dive and have ever since I received my Open Water certification in 1995. Since that time, I’ve done 1,500-plus dives in some of the best diving destinations around the world. I am also 6 feet tall and weigh 265 lbs. By standard definitions I’m an overweight diver.

For several years I’ve worked out routinely with a personal trainer, focusing on strength training, and have had great improvements in strength and endurance — along with weight loss — from those efforts. On my off-training days I try to spend time on the treadmill working on my cardio, while watching some of my diving videos, but I must admit I don’t get that in as often as I should. Scuba diving is a major motivator for my workouts.

I might be an overweight diver, but I am certainly not an unfit diver. My trainer uses upcoming dive trips to motivate me during workouts. For example, when I told him I was going to Bonaire and planned to do many shore dives, we concentrated more on leg workouts to make it easier for me to do the entries and exits in my full gear, which includes lugging along my underwater video system.

I believe all divers need to dive within their training, experience, skill, comfort and fitness levels. I always consider these elements myself when I plan my dives. I also focus on this when I’m teaching any diving student.

I’ve seen many divers — both overweight and “normal” weight — who appear to be unfit to dive based on the above criteria. From my experience, it’s very difficult to tell from looking at the divers whether they are fit enough to dive.

During my two most recent trips aboard Aggressor live-aboards, I encountered examples of both types of divers. On one trip there were a couple of overweight divers (we’re easy to identify on the dive boats!) who had some of the best buoyancy skills I’ve ever seen, incredibly good air consumption and were great at finding all kinds of cool things on the dives. During our surface intervals, I learned they both had rigorous workout routines yet struggled with their weight, something I could certainly relate to.

On another trip there were several “normal” weight people who needed assistance getting their equipment to and from the dive platform due to a variety of knee, back and hip problems. In the water they were great divers, and out of the water very fun people to spend a week aboard a live-aboard.

I recently had a student who was barely able to pass his swim and treading water test, but he did complete the requirements with great difficulty. This student was also able to barely master other skills required to complete his confined water training. I recommended the student work with a trainer to improve endurance and overall strength for diving. No, this student wasn’t overweight, but he was unfit for diving.

From my experience, it doesn’t matter how much you weigh. What matters is whether you are fit to dive.

Marc Weiss is a PADI IDC Staff Instructor, U.S. Coast Guard Master Captain and award-winning underwater videographer.