Avoiding the Low Air Blues: Essential Guide to Scuba Air Management and Diver Safety

There’s probably nothing more important to us as divers than air. We’re air-breathing creatures, and even the best of us, the most well-trained, can only survive without it for a very few minutes. I suspect that for most of us, being suddenly without air for less than a minute might signal the end of a bad day. 

In fact, accident statistics reveal that running low or out of air is a leading cause for rapid ascents and inability of divers to maintain buoyancy once reaching the surface. For these reasons, planning our underwater sojourns, and considering the prospects of a low air or out of air scenario, should be a primary consideration for any dive. 

But the need for conserving our air also comes from the perspective of enjoyment. We’ve all had the experience of having to end a particularly enjoyable dive sooner that we would like due to reaching our minimum air reserve. Wouldn’t it be nice to be able to stretch that time – even by just a few minutes? 

The seemingly obvious solution is to simply use a larger cylinder, but that comes with its own set of issues. Perhaps the better solution is to make more efficient use of the air we carry in order to avoid those low air blues.

Air consumption basics

On the surface, a typical diver might consume in the order of three quarters to one standard cubic foot of air per minute – a rate that varies considerably from one individual to another depending on their size, fitness, and their level of activity. As we descend to depth, we breathe the same volume of air, but since it is compressed, the total mass of air consumed increases. At 10m, we double the air consumption; at 20m it is tripled, and at 30m we’re consuming four times the mass of air. A typical 80 cubic foot aluminum cylinder that might last us 90 minutes at the surface could easily be consumed in just 22 minutes at a depth of 30m. Clearly, our dive planning must take into consideration the limited amount of air we can carry and the depth at which we will be diving.

Another factor we should understand is that not all breathing is the same, and poor technique can lead to increased air consumption. Shallow breathing is less efficient due to the dead air space in our windpipe. Breathing more deeply means we inhale a larger percentage of fresh air. Skip breathing – holding our breath for short periods between inhalation and exhalation – is also less effective in terms of gas exchange, and may not gain us any advantage except over very short periods.

Air planning

In order to effectively plan our underwater sojourns, we need to have a good handle on our personal air consumption, as well as that of our dive buddy. One good way to do this is to document our dives, noting our bottom time, depth profile, and air consumed, along with some data on water temperature, our exposure suit details, currents, and our activity level on that dive. We can then use that information to predict our air consumption for a similar dive in the future, as well as making adjustments to our exposure suit and equipment requirements for a dive. If we’re lucky, we’ll be diving with a buddy who also tracks his air consumption, and has a reasonable handle on what his or her air consumption will be for a planned dive. Next, we can plan the depth for our dive. This is typically based on the location, bottom topography, and our particular objectives for the dive. From the perspective of decompression obligation, it is better (and safer) to do the deeper part of our dive first, and then transition to shallower depths later in the dive. When we make such transitions will obviously affect our total air consumption for the dive. We might decide to move to a shallower area of the site when the first diver reaches a predetermined cylinder pressure. 

An important aspect of our air planning is determining how much to keep in reserve. Cave divers rely on the rule of thirds: one third going in, one third coming out, and one third for emergencies. In open water, we can apply a similar strategy, or we might just set a minimum pressure at which the dive will be terminated. While some divers might use the same reserve pressure (50 bar, for example) as their limit, it might make more sense to adjust that number for the particular circumstances of the dive. With that in mind, we might consider increasing our reserve air limits for deeper dives, colder water, currents, darkness, lower visibility, and the potential for underwater obstacles.

Making our gas last

A number of strategies can help us achieve lower air consumption. First is proper weighting, trim, and streamlining. If we’re over-weighted, then we must add air to our BCD to compensate. As we descend and that air compresses, we must add more air to compensate. Then, as we ascend, that air expands, and we must release air to maintain neutral buoyancy. But if we’re properly weighted to begin with, we avoid all this, and use less air. Trim is also important. If we travel through the water in a near-horizontal position, the drag of our body moving through the water is reduced, and we work less, which translates to less air consumption. So if we adjust our trim properly through the use of trim weights and proper positioning of our cylinder and weight belt, then we can glide through the water with less effort and less air consumption.

Streamlining – eliminating protrusions in our equipment that cause drag while moving – is often overlooked by divers, but is yet another way to make our movement though the water more effortless. Dangling hoses and gauges, and various accessories that interfere with the flow of water past us while we’re diving, easily rob us of precious energy and air. Proper thermal protection is also critical to our air consumption. A cold diver must work harder (have a higher metabolism) in order to keep warm, and thus must consume more air to meet those metabolic needs. Through the judicious use of thermal protection, we stay comfortable and use less air. 

Unnecessary movements and inefficient kicking all contribute to an increase in air consumption. Sculling with our hands consumes lots of energy unnecessarily, so again, proper buoyancy control is essential. We should use a slow, efficient flutter kick to minimize our energy output. Keeping our speed low also reduces the energy needed to get from A to B underwater. Doubling our speed through the water typically requires eight times the energy due to the effects of increased drag, which means we use a whole lot more air. By maintaining a moderate or leisurely pace, we can keep our air consumption in check. 

Another way to conserve air is to avoid frequent depth excursions. Just as when we’re overweighted, up-and-down depth excursions require constant adjustment to our buoyancy, which consumes extra air. Certainly, any dive may require changes to our depth, but if we can keep that to a minimum, and avoid sawtooth dive profiles, we’ll be ahead on air consumption. 

Yet another tip for minimizing air consumption is to perform a leak check prior to diving, and make the necessary adjustments to stop those leaks. That includes such things as O-rings, hoses, and connections such as for our BCD inflator. And of course, we need to make certain our regulators are not free-flowing – not even a little. Especially at depth, even minor leaks can eat into our air supply more than we might expect. 

Finally, we need to minimize stress in order to keep our air consumption in line. Three primary factors can help us reduce the stress of diving. First, a diver who has better physical fitness will expend less energy when exercising, and that’s important for us as divers. Following a routine regimen of training – preferable some exercise that we can enjoy – will help us maintain proper weight and physical fitness, which helps us on our dives. 

Along with maintaining fitness comes a need to maintain our diving skills. We need to have the proper training for the environments in which we will be diving. Moving out of our comfort zone into a more-difficult and demanding situation raises our stress level and our air consumption. It’s important to stay within our limits, and get the proper training before we tackle the more demanding environments.

Diving frequently can also help keep our stress levels in check. Repetition breeds familiarity, and with that comes a lower stress level, which translates to a lower breathing rate. Remember that any time we become stressed, our air consumption increases. 

To keep our air consumption in check, we need to keep calm, and be conscious of our breathing. If we find our breathing rate getting high, we should try to calm ourselves and focus on proper breathing.

Breathing in a pinch (when air runs low)

The first thing to do when running low on air is to signal our buddy, get to a shallower depth, and slow the pace to reduce air consumption. We should also leave some air in our cylinder to manage a difficult situation near the surface, or to navigate rough conditions for a shore exit. 

In the old days, divers were taught to buddy breathe, which involves passing a regulator back and forth while making their way to safety. This manoeuvre, while easier when sitting at the bottom of a pool, can be a bit difficult in open water, particularly when one or both divers are stressed. The standard remedy for a low-air scenario now is to share air, either with a buddy’s octopus or alternate air supply. This is a highly viable strategy, but works much better if the two of divers have practiced the skill and can manage its potentially awkward movement. 

Having the right equipment (a longer hose on the alternate air/octopus) makes the procedure much easier to perform. Typically the spare regulator is brightly colored and is located in the upper chest region of the donor diver where it can be easily seen and retrieved. In some scenarios, a near-panicked diver will grab the regulator out of his buddy’s mouth, and the donor (who is presumably calmer) can switch to the spare regulator – at least to start with. 

An alternative to (or in addition to) the octopus/alternative air system is to carry a redundant air supply – either a small emergency breathing device, or a pony bottle or ‘bailout bottle’. Pony bottles come in a variety of sizes to suit a diver’s needs, and are equipped with a standard two-stage regulator. They are typically strapped to the primary cylinder, or attached with a harness below the diver’s BCD. Either way, it provides a diver with a failsafe supply of air to extract oneself from a demanding underwater situation and return safely to the surface. 

The key to success for air sharing is practice. The more we practice, the more proficient we become, and the process becomes easier and less stressful. Many instructors recommend practicing air share drills on each dive, either at the beginning of the dive to sharpen our skills, or at the end of the dive when we’re making a safety stop or just using up some of our reserve air. 

It’s fair to say that none of us wants to run low or out of air on any dive, or to end a dive before we finish what we set out to do. The keys to avoiding such a scenario really come down to planning, efficiency, and maintaining a low stress level. Just a little bit of knowledge and planning can go a long way toward avoiding the low air blues.

Did you know?

Diving air consumption is primarily influenced by depth, physical exertion, and stress, which increase consumption significantly!