One Myth Persists
Today back-inflation BCs are everywhere, as are power inflators and integrated weight, first pioneered by the At-Pac over 30 years ago. Modern back-inflation BCs still share some of the At-Pac’s limitations — chiefly the tendency of the wings to wrap around the sides of single tanks, trapping air. The other thing which has not gone away is the debate over unconscious divers floating face down.
One manufacturer, in particular, is convinced that divers who used back-inflation BCs with lightweight single tanks are in grave peril should they suddenly lose consciousness on the surface and their inflated BCs push them into a face-down position. Ironically, his company makes the very type of BC he feels puts divers at risk.
His “solution” to this perceived problem is not to switch to a different sort of BC design for single-tank diving. Instead, he promotes something called a ballast mediated airway. It entails clamping a heavy, non-ditchable weight to the back of the diver’s tank in an effort to prevent the BC from pitching the diver face forward.
Okay, this is not a bad guy. He clearly means well. The irony is that he is also a promoter of DIR (“Doing It Right”). Among the core principles of DIR is that you don’t complicate equpment by attempting to solve non-existent problems.
If all divers did was sit around on the surface, by themselves, waiting to pass out, this guy’s idea would have merit. Real divers, however, spend the majority of their time under water, swimming in a face-down position.
When in a normal swimming position, physics dictate that the most ideal configuration would be to have a diver’s ballast concentrated as close to his or her center of gravity as possible, to combat the adverse effects of polar inertia. Baring this, the weight should be concentrated below anything such as a BC air cell. If, in contrast, you place weight at the top of the stack, it will tend to force divers to turn turtle.
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