A diver using rented equipment felt he was not getting enough air at depth. He tried buddy breathing but had little improvement. A divemaster came to the rescue by sharing his octopus, and they did a controlled emergency ascent.
While diving with a hard-breathing rental regulator at 141 fsw, I suddenly felt I could not get air. I went to my octopus, and it was no better. Then I went to my buddy’s octopus; it was a little better but still not good. The divemaster noticed that I was having problems and gave me his octopus, then he and I performed a controlled emergency ascent. (Note: The 64-year-old diver is 6’1″ tall and weighs 210 pounds. His diving experience is not reported.)
Some dive shops may not maintain rental dive computers well, and some regulator models do not perform well in deep dives even if they are perfectly maintained. Remember, at a depth of 141 fsw (43 msw) the pressure is 5.2 ATA — it is 5.2 times greater than at surface at sea level. For the same volume of breath, the regulator has to deliver five times more molecules of gas against proportionally increased resistance. If a regulator is not properly designed or maintained, it fails to deliver the necessary volume. The diver will feel that the regulator is “hard” or just feels air hunger. In this case, it appears that the regulator felt “hard” even before reaching 141 fsw depth, but the diver proceeded deeper regardless. That was not a wise decision.
Divers diving deep such as in this case would do best to carry their own regulator they have tested before, serviced regularly and properly maintained between dives.
Marty McCafferty, EMT-P, DMT