Scuba Q and A:
How Can I Make My Air Last Longer When Diving?
Q. I normally finish my air before everyone else. How can I conserve air when I dive?
There are several factors that dictate air consumption. Let’s examine them:
This is something you cannot change. Different people have different vital lung capacity (i.e. litres/cuft) – women tend to be better than men. Body size (frame, not BMI) also has a direct impact. You have to live with this.
Your rate of breathing (time to inhale/exhale) has a big impact also. This rate is determined by several factors; such as your cardiovascular fitness, your state of relaxation or tension, the workload that you are subjected to. More about these later. Good breathing habits also help – developing a natural, but deep (stomach) breathing pattern helps flush CO2 from the lungs and lowers respiration demand.
An article about respiration and gas management techniques: Scuba Breathing and Buoyancy
Air consumption varies with depth. The deeper you go, the more gas you use from your cylinder. This is because the density of air your breath is proportionally linked to the ambient pressure surrounding you. For example, at 10m (2ata) you consume double the gas, per breath, that you would do at the surface. Dive shallow to extend your gas duration.
A reminder on the Scuba Gas Laws: Simple Gas Physics For Divers
The larger the gas supply, the longer it will last. Choosing a larger capacity and/or higher pressure cylinder can compensate for higher gas consumption. Modern options like sidemount diving offer recreational divers access to much larger gas supplies (two cylinders).
Learn about Sidemount Diving: Sidemount Training
The body metabolizes oxygen more or less efficiently depending on your fitness. This becomes more significant as your workload increases. Improving your physical fitness means you can dive harder, with less increase in your respiration rate.
Workload and Exertion
This is directly linked to your cardiovascular fitness, but can also be tackled as a separate issue. Reducing your workload reduces demand for oxygen and decreases respiration rate – lowering gas consumption. You can significantly decrease your workload by achieving better buoyancy, trim, streamlining…and fining at a slower pace. Understand that increased speed causes a disproportionate increase in water resistance, hence a disproportionate increase in workload. You might also consider developing alternative fin stroke methods, such as a relaxed ‘frog kick’ that employs a graceful ‘kick-and-glide’ motion.
See my article series: Buoyancy Masterclass for some good tips.
Tension, Relaxation and Stress.
Your psychological state is just as important as physiological factors. Tension and anxiety cause increased respiration and higher air consumption. As a diver gains experience, they grow more comfortable and this leads to less air consumption. This is a factor that improves with time/experience, but can also be somewhat determined by diving well within your comfort zone.
One of the major causes of tension in divers with poor air consumption… IS THEIR AIR-CONSUMPTION. People can stress out over being the ‘gas guzzler’ and this causes a circle of tension that further deteriorates their gas consumption rate. One of the best improvements I made to my gas consumption, as a novice diver, was when I just quit worrying about it and accepted it for what it was. All of a sudden, I used a lot less gas on each dive. Miraculous!
About the Author
Andy Davis is a RAID, PADI TecRec, ANDI, BSAC and SSI qualified independent technical diving instructor who specializes in teaching advanced sidemount, trimix and wreck exploration diving courses across South East Asia. Currently residing in ‘wreck diving heaven’ at Subic Bay, Philippines, he has amassed more than 9000 open circuit and CCR dives over 27 years of diving across the globe.
Andy has published many magazine articles on technical diving, has written course materials for dive training agency syllabus, tests and reviews diving gear for major manufacturers and consults with the Philippines Underwater Archaeology Society.
He is currently writing a series of books to be published on advanced diving topics. Prior to becoming a professional technical diving educator in 2006, Andy was a commissioned officer in the Royal Air Force and has served in Iraq, Afghanistan, Belize and Cyprus.