You? Run Out of Air? Impossible . . . Right?

While experienced divers rarely run out of air, it's a foremost concern of dive trainees, and it can happen if their instructors are lax or casual about monitoring them. That's why we divers normally dive with a buddy, and that buddy carries an alternate air supply (an octopus), for such an unlikely emergency. For solo divers, a redundant air supply should be a must. After all, there is rarely a valid excuse for an experienced diver running out of air.

Many experienced divers use air-integrated computers that not only display remaining tank pressure, but also calculate how long the remaining air will last at the current depth and breathing-rate. By keeping the remaining air time greater than the remaining no-deco-stop-time or the displayed ascent-time (including mandated stops), you shouldn't get into trouble.

I remember well an over-enthusiastic French dive guide in Tahiti insisting on taking me down to 165 feet to see some puny gorgonia sea fans, and later leaving me to eke out the last dregs of air from my single tank at a mandated deco-stop. There's no fool like an old fool, and with several thousand dives under my belt, I should have known better.

We often find ourselves paired with a buddy we have not met before and don't know how he would react if one of us needed help. Do you take the trouble to check that your buddy's octopus works properly before a dive? Do you check that your buddy's octopus is rigged in such a way that it is readily usable? Or if the hose is long enough for the job?

Too many divers don't.

Does Buddy Breathing Work?

In the early days of dive training, buddy breathing was taught in urgency because training agencies felt it too onerous to ask divers to fork out for an alternative second-stage (an octopus). It was a confidence-building exercise, often practiced in the pool and part of the basic course. The donating diver needs to trust that the other diver will part with his her regulator after a couple of breaths, which is not always the case if stressed by being out of air.

It was never a panacea for being out of air. In real crisis situations, divers often lost sight of their depth, concentrating so hard on the breathing exercise that they dropped deeper, ending in a tragedy usually described later as "a failed attempt to buddy breathe."

Spare Air = Small Hopes

This tiny little tank has been marketed to divers for many years as a viable alternative air supply. It was developed originally for shallow-water escape by helicopter crews that might ditch in the sea and need to escape from an inverted helicopter. Many divers still carry them as a confidence-boosting device, but if you run out of air deeper than, say, 30 feet, the small amount of air contained within them will not take you far.

Years ago, I tested a Spare Air for Diver magazine in the U.K. and determined there was insufficient air to get me safely from 100 feet deep. I called my article "Three Breaths from Death."

In May 2001, an article in Undercurrent noted that a full standard Spare Air might supply enough for a hasty ascent from 60 feet. However, such a fast ascent might be an invitation to decompression sickness, and there would be little scope for a 15-foot safety stop. Even then, it requires a timely decision and a slick deployment.

If you carry a Spare Air (or newer, similar devices such as Sea GoW, Skorki and Mini Dive), be aware of its depth limitations and that it does not come close to the performance of your primary regulator. Heaving it open by sucking on such a poorly performing regulator valve can be too hard in a stressful situation. To understand how difficult it is to breathe, test it at depth next time you go diving.

In previous Undercurrent issues (November 2015 and January 2016), we published comments from some Undercurrent readers who believe their Spare Air could be a lifesaver. It can be, but a user must understand its limitations. Don't expect to be able to undertake a safety stop, either, if in dire straits. Carrying one is more an act of faith than a practical solution to an out-of-air crisis. It is not a panacea.

Of course, it makes sense to test every redundant air source at the beginning of every dive, but these small devices contain so little air, if you did that, you would deplete it.

If your primary regulator did fail, it has been designed to fail in the open position, resulting in a dramatic increase in the inter-stage pressure. If the second-stage were to fail (most likely caused by this dramatic increase in inter-stage pressure), it is designed to free-flow, and every diver should know how to make a controlled ascent breathing from a free-flowing regulator. (It's covered in the basic openwater dive course.)

The Best Thing to Bring on Your Dive

Many European divers use a double tank valve (on a single tank) that allows the user to fit an independent redundant regulator or, more often, a totally redundant air supply in the form of a second smaller emergency cylinder -- a pony tank around a quarter the size of the main cylinder -- clamped to the main tank and bearing its own regulator. Some American divers are picking up on the idea of a pony, especially those making more serious dives.

Should the main air supply fail (usually by mismanagement rather than a rare catastrophic mechanical failure), the diver can switch to the emergency pony tank and make a safe ascent. That's the way it's supposed to work, but it doesn't always. There have been cases where divers confused the two regulators and erroneously began their dives breathing from the pony tank, thinking it was their main tank. They unexpectedly ran out of gas from the tiny tank, failed to switch to the main cylinder and tragically drowned.

Last fall, an experienced diver who joined a Power Scuba charter on Pacific Star out of San Pedro Harbor near Los Angeles, made that error when he began his dive on an oil rig. Evidently, he lost consciousness at 100 feet, about 10 minutes into the dive, and after being taken to the surface, he could not be revived.

Ken Kurtis of Reef Seekers (Beverly Hills, CA) reports that an investigation into the fatality found that the diver's 19-cu ft. pony was empty, yet his 105-cu ft. main cylinder was untouched, indicating that he probably breathed from the regulator attached to the pony, thinking it was the regulator attached to his main supply.

Pony tanks are rarely fitted with an accessible gauge of their own. So had the diver checked his air gauge, he would he would have seen that it remained fixed as if his tank were full (e.g., 3000 psi), even though he had been diving for 10 minutes. We suspect that it was so early in the dive, he assumed no need to do so. Lulled into a false sense of security, he lost his life.

What do we learn from this? If you use more than one regulator, you must have a positive way to identify which is which. Using more than one tank is the first step toward being a technical diver, but a trained technical diver is careful to mark each second-stage differently so that he can tell one from the other. His life depends on it.

A pony tank can give you added security, but only if you use it properly. Always be aware which regulator is in your mouth. Your life might depend on it.

-- John Bantin