Turning the tank valve back half-a-turn often confuses divers and can inadvertently make breathing difficult at depth. This diver kept a cool head and ascended on her buddy’s alternate air source.
Historia reportada
While diving with my dive buddy in Florida, I noticed that upon each inhalation the needle of my submersible pressure gauge (SPG) fluctuated. The needle dipped down with each breath before returning to the correct psi reading for my tank. I continued diving while keeping a close eye on the gauge and, upon reaching a depth of approximately 55 feet, (16 meters) it suddenly became very difficult for me to breathe. I looked at my SPG mid-breath and saw the needle drop down to zero psi, and it did not readily move back up. I felt like there was no more air available to me even though I knew there was at least 1200 psi (80 bar) in my tank. I signaled “out of air” to my buddy, and used her alternate regulator. We made a controlled ascent to the surface, and I was not injured. Upon inspecting my gear, I realized that instead of turning my tank all the way on and half a turn back, I had turned it all the way off and half a turn on. Upon reaching a depth below 33 feet (10 meters), I had experienced inadequate air pressure delivery from my tank to my regulator because the tank was barely on and could not continue to deliver the same volume of air at the increased pressure.
Comentario
It must have been disconcerting to suddenly be unable to breath at 55 feet (16 meters) depth. This diver kept a cool head, signaled “out-of-air” to her buddy, secured the alternate air source and made a controlled ascent. This is exactly what is taught in entry-level diver courses worldwide.
Los días en los que necesitábamos girar la válvula media vuelta hacia atrás han quedado atrás, pero todavía algunos instructores enseñan a los buceadores a hacerlo. ¿Por qué? La forma más segura de asegurarse de que dispone de gas suficiente para cualquier inmersión es abrir la válvula de la botella hasta el fondo y, a continuación, mirar la SPG mientras respira un par de veces.
If your needle does not move then your valve must be open and if your needle goes down towards ‘Zero’ then your valve must be closed. If you are in the habit of turning it back half-a-turn then, like this diver discovered, you might have enough gas to breath normally at the surface but you could find yourself short of breath at depth. Remember, the safest way is to turn your tank valve all the way open or all the way closed.
Peter Buzzacott, MPH, Ph.D.