Technical divers employ all sorts of redundant equipment, including redundant air supplies. This only makes sense; entering caves and wrecks, or diving to depths well beyond those most recreational divers will ever experience calls for redundant equipment of all kinds. The question is, should the rest of us have a plan, or should we simply hope for the best?
Personal Responsibility
While we all have a modicum of personal responsibility during all aspects of our topside lives, the weight of this responsibility increases with each and every meter of depth we attain. Self-reliance is the key to survival in the ocean's depths, and one of the best ways to keep ourselves out of harm's way is to carry a redundant air supply. Simply put, carrying a redundant air supply provides us with a backup plan.
Along with personal responsibility comes the freedom to choose your own redundant air supply, instead of settling for some kind of "one size fits all" solution mandated by a regulatory board, all in the name of eliminating preventable death from the list of possible dive outcomes. While all divers should carry spare air, personal choice in the matter should not be eliminated.
When Redundant Air is Necessary
A redundant air supply is viewed by some as a burden. If you're one of these people, it's time to reevaluate your thoughts regarding the importance of carrying a secondary air supply. Underwater, there are no filling stations that supply air to divers who are running low. Buddy breathing in an emergency is no picnic at best, and when you're out of air, making it to the surface is a risky proposition in itself. While most of us will probably never experience a situation that calls for secondary air supply use, its simple presence can provide us with a safety net in the event any number of crisises occurs. You might not use it yourself, but you could save another diver.
Some situations absolutely call for a secondary air supply. Any time you're diving beneath a ceiling, for instance, redundant air is a necessity. If you use a rebreather, you need bailout air, too. If you have a tendency to become fixated on underwater functions like hunting or photography, spare air is something you definitely need to add to your kit.
Choosing a Redundant Air Supply Source
When selecting a redundant air source, the size of the source should correlate directly to the type of diving that you do. It only makes sense. Attaching a pony bottle to your cylinder band, inspecting it prior to each dive, and practicing its deployment is a good strategy for most sports divers. Obviously, deep divers and mixed gas divers will have different redundancy requirements.
To pick the redundant air supply source that is going to work best for you, enlist the aid of diving professionals: your instructor, your local dive shop, a resort operator, a divemaster, or even a dive boat captain can help you to select the source that is right for you. Long story short, the gear you use should be enough to bring you down and back up again safely, no matter what happens while you're underwater.
Even when you have chosen a redundant air supply and put it into use, you should remember to continue keeping up with your skills; continue to practice buddy breathing and self-rescue skills, always make a dive plan, and never fail to stick with that dive plan. Maintain your equipment properly, and hope you'll never need to use that extra reserve. While the choice is up to you, making the right decision is never the wrong thing to do.