This month’s scuba class just got to the part about out of
air emergencies. I think that this was a
particularly compelling topic, as the air depletion exercises in confined water
were fresh in their minds. In The
Complete Diver, Alex Brylske cites a DAN study of 1000 diving fatalities,
in which 41% were the result of the diver running out of air. DAN reported that 70% of the accidents
occurred at depths shallower than 100ft, 40% in the range of 60-99ft, and 30%
shallower than 60ft. One third of the fatalities
occurred in depths in which even the newest of divers would feel safe. So what gives?
Where were these divers’ buddies? I tell my divers that their buddy should
always be visible (don’t get too far apart, especially in low visibility) and
in clear water should never be farther than you can swim on one breath of
air. It is easy to address an out of air
situation if your buddy is near and equipped with an alternate air source.
What if your buddy is not near? We are all taught the CESA (or CSA, controlled
swimming ascent), controlled emergency ascent in open water class. In case any of you do not remember, it is one
in which when the diver realizes that his air is depleted, and his buddy is not
near. The diver then looks up (who wouldn’t), opening his
airway. He lifts his inflator hose in
the air to vent air from his BC to control the ascent, and starts swimming for the surface (duh) saying
“AHHHHHH”, or humming, or in some way letting
a continuous stream of bubbles escape his lungs. Allowing the air out seems counterintuitive,
but this is the part that keeps someone who is out of air from becoming a
fatality. Boyle’s law applies even if
you are out of air. As the diver ascends, any gas in his system starts to
expand. Air that remains in your lungs
or body spaces will expand as well. If
the expanding air in the diver’s lungs (alveoli) is not allowed to escape through
the airway, the expanding gas will eventually rupture the lung. Since the gas will find a way out of your
body one way or the other, it is in the diver’s best interest to do it the easy
way and allow the gas to simply exit his mouth.
Now it is important to note, that through this process, the regulator STAYS IN THE DIVER’S MOUTH. This is key for two reasons. First, if the regulator is in the diver’s
mouth, water cannot get into his lungs.
This is a good thing. Second, it
is important to remember that when the diver failed to get air when he inhaled,
there was likely SOME air left, but it was at such a low psi that he could not draw
it into his lungs. As he makes his
ascent, that air, like the air in the diver’s lungs, expands, perhaps providing
the diver with another breath. If a
diver is practiced at this procedure and is able to remain composed in the face
of an out of air emergency, he should be able to manage a safe ascent and save
himself. Do you practice, even mentally,
for out of air situations?
I suppose that this is a skill that many divers simply
forget about after certification with a vow to never forget to check their
pressure gauges, but here’s the kicker: In DAN’s study, there were two groups
of divers who had the most accidents; as one would expect, divers with less
than 30 dives and unexpectedly, divers with many (hundreds) dives. In the less experienced group, I would assume
that the diver found himself out of air due to poor planning, poor decision
making or inattention to gauges. When
the diver discovers his error, either he forgets his training or panics. In the experienced group, however, I would
bet that at least some of the situations arose out of a laissez faire attitude,
or out and out arrogance. The first few moments of the emergency are taken up
with the diver thinking, “I can’t believe this is happening to me!” The rules
of supply and demand apply to all divers without regard to experience. An equipment problem such as a leaking high
pressure hose is just as dangerous for an experienced diver as it is for a new
diver. Experienced divers should return
to the boat with a reserve the same as a new diver because unexpected events,
such as reverse squeeze, can happen to anyone and one never knows when that
reserve will change from a cushion to a life saver.
I guess the take away is this: It is possible for any diver
to find himself in an out of air emergency, but preparing oneself for this can
be the difference between life and death.
Follow these rules and you will increase your safety tremendously:
1.) Check your SPG often.
2.) Stay close to your buddy. Alternate air source ascents are
easy and will allow you the best chance to complete your safety stop.
3.) Pay close attention to your gear’s maintenance. Address even
small repairs as soon as you discover them.
4.) Rehearse out of air scenarios during pool reviews, in
shallow open water or at least in your mind.
5.) Review your open water video, or search Youtube for some demonstrations.
