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Tips for Improving Air Consumption

New DMT’s often complain of having excessive air consumption and being unable to stay as long as their more experienced coursemates.  Here are a bunch of tips:

 

  • Streamline your equipment. Place accessories in pockets or leave them behind. Shorten your hoses (where you can) and keep them close to your body. Clip in your console and your octopus. Choose a properly sized BCD – “too much BCD” causes excess drag.
  • Keep it small. When taking spares, use accessories which are small or designed for pocket storage.
  • Drop weight. The less weight you carry, the less air you have to put into your BCD to maintain buoyancy, which means you have less bulk that you have to drag through the water.
  • Get neutral. Neutral buoyancy, combined with PROPER TRIM will keep you horizontal, and that means you move less water, which in turn means less drag.
  • Slow down. Water resistance increases exponentially with speed. Swimming twice as fast requires four times as much energy. All your movements should be in slow motion.
  • Use efficient fins. Some deliver more thrust for a given effort than others, especially split fins.  Cheap, flexible fins are not going to help you.
  • No hands. Use your fins. Swimming with your hands is very ineffective, and causes you to work harder which in turn uses up your air faster.
  • Don’t skim the bottom. If you are close to the bottom, going around or above the contour will cause you to expend more effort than a diver a few feet higher.  Effort = wasted air.
  • Make long surface swims on your back. Breathe surface air: It’s free. Did you bring your snorkel?
  • Pause after inhaling. Under water, your breathing pattern should be inhale, pause, exhale, inhale, pause, exhale. THIS IS NOT “HOLDING YOUR BREATH”! The pause (held with your chest muscles, not by closing your throat) allows more gas transfer to take place in your lungs and less oxygen to be wasted.
  • Breathe slowly. Friction between the incoming air and your mouth, throat, lungs, etc. increases exponentially with speed. More friction means more energy expended for less air actually arriving in your lungs. Move the air slowly.
  • Breathe deeply. The more complete each breath is, the fewer of them you have to take. Breathe “from the diaphragm,” trying to completely fill and completely empty your lungs.
  • Use a high-performance regulator. Better regulators minimize the work of breathing. They minimize the amount of air you burn just getting air.
  • Maintain your regulator. They lose performance and increase work of breathing with use and age, and need regular maintenance.
  • Readjust your regulator. On many regulators, the purpose of the adjustment knob is not merely to prevent free-flowing on the surface. It’s also to minimize work of breathing at depth. Periodically during your dive, open the valve until the regulator just begins to bubble, then back up on the adjustment a bit.
  • Keep warm. The colder you are, the more energy your body uses – and so the more air you’ll guzzle. Remember that you lose heat from your body around 20 times faster in water than in air, so make sure you wear adequate exposure protection to avoid getting too cold.
  • Stop all leaks. Lots of little bubbles add up. Check the usual suspects: tank O-ring, BCD inflators, console swivels.
  • Stay above your buddy. At five feet less depth than your buddy, you’ll see almost everything he does, but you’ll use substantially less air. (Though the difference is greatest at shallower depths.)
  • Manage currents wisely. Learn how to detect, avoid and cope efficiently with adverse currents.
  • Relax. Perhaps the biggest factor – reduce your stress and just enjoy the ride; by reducing your workload under the water, you’ll reduce your air consumption vastly.
  • Dive more. The more diving you do, the more familiar your equipment will feel, the more comfortable you’ll feel in the water and therefore, the more relaxed you will be on your dives
Diver on the left is poorly trimmed, pitching up, thus drawing more water, creating more drag, and possibly floating up.  Driver on the right does not have these issues.
Diver on the left is poorly trimmed, pitching up, thus drawing more water, creating more drag, and possibly floating up. Driver on the right does not have these issues.

Diver trim is one of the most important factors setting your air consumption (only surpassed by gear problems and diver stress) .  If you are carrying excessive weight, especially on a belt which is located below/behind your centre of mass, this will cause you to pitch up and not be horizontal. In that position you create a tremendous amount of drag which then requires a tremendous amount of effort.  Having proper weight and proper weight DISTRIBUTION will easily reduce that drag, thus reducing effort, and therefore air consumption.  Keep in mind, however, that as an ASSISTANT, you should be a little bit on the heavy side in order to be able to control novice divers.