Objective: Experience the sensation of increased breathing resistance from a scuba regulator as it begins to run out of gas and progresses to the point where it delivers no gas at all.
Value: Although divers are taught gas management techniques to ensure they do not actually arrive at an out-of-gas situation, experiencing the sensation immediately prior to a regulator delivering zero gas can be very instructive. The feeling of increased breathing resistance at depth is something you may also experience if a scuba cylinder’s valve is not fully open. Your reaction then would of course be to get your buddy’s attention as you reach back and open it fully.
How It's Done:
- Kneel in water shallow enough to put your head well above water when standing.
- Your instructor will face you and ask if you're OK and ready.
- Return the OK hand sign, and watch your SPG.
- Your instructor will gradually turn off your tank valve.
- Watch as the pressure indicated by your SPG falls to zero.
- Stay calm as your gas supply is depleted.
- Signal to your instructor when the gauge reaches zero, and he or she will turn your air back on. (You may find this skill more comfortable without fins on your feet.)