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The Private, Exclusive Guide for Serious Divers Since 1975
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September 1999 Vol. 14, No. 9   RSS Feed for Undercurrent Issues
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How to Emergency Breathe From a BC

from the September, 1999 issue of Undercurrent   Subscribe Now

To gain confidence in your ability to act in an emergency, practice this and all of the other BC breathing skills with your gear in shallow, calm water. Be sure to disinfect your BC first.

Clear your mouthpiece. Most current inflator hose mouthpieces have openings for easy purging, so the best method is to tilt the end of the mouthpiece down and blow a little air in so the water runs out of the holes. This will take only a small puff. Hold the valve down as you continue blowing. Your exhaled breath will now go into the BC and the holes will be sealed so no water can re-enter. Donít release your tight hold or water will leak back in through the holes. With older models, bend the mouthpiece up, seal your mouth, look down, and, as before, blow air in as you push the valve. The water will flow from the mouthpiece and become trapped in the hose, but air will be able to get past it.

Take your first breath cautiously. Inhale slowly and carefully. If you do cough or strangle on a few droplets, donít remove the mouthpiece or youíll just have to go through the clearing process again. If you must cough, cough into the BC. Control your ascent. Exhale normally and watch your ascent rate, because whether breathing from your tank or BC, you still face the danger of an embolism if you retain air that youíve breathed at ambient pressure. Donít let go of the valve or remove the mouthpiece from your mouth as you ascend. Releasing your hold on the valve of a mouthpiece that has no holes will not allow water to enter, but it will cut off your air from the BC. Avoid overfilling your BC as you rise by exhaling through your nose. Flaring out horizontally will also help slow your ascent. If youíre sharing air with a buddy, be sure his BC doesnít overinflate either.

Using air from your tank. As long as your power inflator is working, you can add more fresh air to your BC as you rise, and you can continue to breathe that air at ambient pressure. Keep the mouthpiece valve closed tightly while putting air into your BC so none escapes. Open the valve from your tank intermittently, take a breath, and exhale it through your nose to insure a continuous supply of fresh air. Practice till youíre confident that in an emergency you can handle both valves simultaneously.

You can also breathe from your BC while a buddy is breathing from your tank. Since your power inflator bypasses your regulatorís first stage, you can inhale from the BC at any time without over-breathing. If your buddy is in danger of over-breathing the second stage youíve shared with him, wait to feed air into the BC until you see his bubbles. Keep feeding air in intermittently between your buddyís inhalations, and try to calm him down.

With no air available from your tank. As we stated earlier, air in your BC will expand as you rise just as air in your tank does, allowing additional breaths as ambient pressure decreases. Start up immediately, keep trying to inhale and exhale, and air will become available. If you have a BC-mounted safe second such as the Air II, you can access the air in your BC by pressing the deflate button when inhaling. In one study, basic scuba students were able to rebreathe this way for a minute in a 10-foot-deep pool with no problems. Staying relaxed is a crucial part of this exercise, because rising CO2 levels will cause you to breathe faster and faster, which could lead to a sudden blackout.

Sound complicated? The industry obviously thinks so. Still, although no oneís going to force you to learn these new skills, one day you might be glad you or your buddy did.

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