WHY DO I USE SO MUCH AIR?

Understanding Air Consumption

Air consumption is an interesting phenomenon. The more a diver huffs and puffs, the quicker his air supply is depleted. Air supply is expressed in pounds per square inch (psi), or bar (unit of pressure), but when you get right down to it, divers are more interested in how many breaths are in the tank or how long it is going to last. Of course breaths per tank is not a constant measurement, because divers do not breathe at the same rate.
The amount of air a diver uses begins with the diver's physique. Generally speaking, the larger the diver, the more air he or she consumes. Smaller divers tend to use less air. This is not always the case, but the majority of the time it holds true.
If two divers sit on shore breathing from same-size, equally filled scuba cylinders, after a few minutes both will have reduced the psi remaining in their tanks, but one will have used more air than the other. Air consumption is an individual matter; even out of the water, each diver uses his air supply at a different rate.
Having established that fact, let's go diving. The deeper in the water column a diver descends, the more air he will use. This is because as a diver descends the ambient pressure - the pressure that surrounds him - increases. As all divers learn during their initial scuba certification, at 33 feet (10 m) the ambient pressure is double what it is at the surface; at 66 feet (18 m) it's three times greater than at the surface.
Consequently, at a depth of 33 feet (10 m) divers consume twice as much air as they do on the surface. At 66 feet (18 m) they consume three times as much as when sitting on shore breathing from the regulator. So, our air consumption is affected by depth - the deeper we dive, the more air we will consume.
The third factor that affects a diver's rate of air consumption is physical exertion. The harder a diver works while underwater, the more air he will use. I use the word work in the context of the physical demand that is placed on the diver's body. The greater the demand, the more air the diver will require to sustain normal body functions.
Physical demand is created in a number of ways. Similar to walking rapidly versus moseying, swimming fast as compared with leisurely taking one's time exploring the reef places more demand on a diver's body and thus requires more air.
Swimming against a current is comparable to running uphill. Struggling to free a stuck anchor is like changing a tire on a car. Improper body alignment - not being streamlined - increases drag and resistance in the water. All of these activities place greater physical demand on your body and thus require more air, whether you are on land or at depth.
Physical demand affects each of us differently. An Olympic athlete may not find any of the above tasks physically demanding, but on the opposite end of the spectrum a person in poor physical condition may find that even the slightest task raises his breathing rate.
A diver's physical conditioning is important, but even the best-conditioned athlete must face the psychological side of diving. This, too, can have a profound effect on the amount of air a diver consumes.
Think about the last time you were nervous over something. Nervousness triggers a host of physiological responses, including an increase in pulse and respiration rates. Divers who are apprehensive and nervous use more air than someone who is confident and relaxed.
The last major factor that influences a diver's air consumption is what I call "the fidgets." A diver with the fidgets is constantly exercising his buoyancy compensator's (BC) inflate/deflate mechanism. Add air, let it out. Add air, let it out. Establish neutral buoyancy, become slightly negative, become too positive, etc. The more a diver fidgets with his buoyancy control, the more air he is going to waste and therefore, the more air he uses. Constantly clearing a mask also uses additional air.
The key things to remember about air consumption:

1. Everyone does not consume air at the same rate while using scuba;
2. The deeper you go, the more air you use;
3. The greater the physical demand on your body while diving, the more air you'll use;
4. Physically fit divers tend to use less air than those who are out of shape;
5. If you are apprehensive about using your air quickly, you probably will;
6. Fidgeting away air - wasting it - contributes to poor air consumption.

Improving Air Consumption

I have not known a new diver whose air consumption did not improve with experience, either as he became more comfortable at depth or through overt changes in his diving technique. There are a number of ways to improve air consumption, many of them interrelated. Let's examine them.
The one sure thing that any diver can do to improve air consumption is reduce drag. Drag is the resistance encountered as you move through the water. The greater a diver's drag, the more effort he'll expend. Increased effort means increased air demand. And there goes your air consumption.
A streamlined diver has minimized drag. Begin by securing all accessory gear close to your body. Fasten up your gauge console and octopus. Place your slate inside a BC pocket. The goal is to make your underwater profile like that of a dolphin - sleek and smooth.
Once your equipment is streamlined, focus on your swimming technique. Streamlined divers take the form of a torpedo. Their head, torso, legs and fins are on the same horizontal plane, here again, sleek and smooth. Their arms are at their sides or folded across the torso.
Energy-efficient divers cut through the water slowly. They employ an efficient kick and breathe long, slow and relaxed breaths. Every movement is deliberate and designed to generate propulsion using the least effort. They adhere to the planned profile and go no deeper than is necessary to accomplish their objective.
Energy-efficient divers do not fidget with their inflation/deflation mechanism. Once neutrally buoyant at the planned diving depth, they often use variations in lung volume to keep their depth constant. If they must rise a few feet to pass over an obstruction they simply breathe a little deeper. They then breathe shallower to return to the original depth. Fidgeting with the inflate/deflate mechanism is not something normally done by divers who have better than average air consumption.
Reducing the amount of weight you wear is another first step to reducing air consumption. A properly weighted diver has a horizontally oriented position in the water column, not a diagonal one in which the head and upper torso are higher than the legs. Overweighted divers plow through the water diagonally as compared with gliding horizontally. It takes much less effort to glide. To achieve neutral buoyancy, overweighted divers must add extra air to their BC. This buoys up their upper body and makes plowing that much more physically demanding. Weight yourself properly and your air consumption will definitely improve.
Using the proper equipment for the environment is another way to avoid quickly sucking down your air supply. Wear the proper thermal protection. Cold divers use more air because their bodies have to work harder to maintain core temperature. Stay warm and your air will last longer.
One air conservation technique that is easier to talk about than to achieve is relaxation. The more comfortable you are underwater, the less air you use.
Slowing down, breathing slowly and making every movement count will help you relax. Once you reach the bottom, stop, close your eyes and spend a moment or two breathing evenly.
Knowing that air consumption increases when demands are placed on your body, being in good physical condition raises the bar on what qualifies as a demand. Divers who are physically fit react to demand better than those who are not. If you are in good physical condition, you are going to have better air consumption.
Even experienced divers can benefit from these techniques to monitor and improve air consumption, so don't be embarrassed if you run low on air before your buddy. Start experimenting with these consumption-lowering techniques on your next dive. You'll be glad you did.

Check out my other page on: How to determine your air consumption rate.