I was taking a break from exams and reading the DAN Incident Report (For those of you who are members, read it. For those who aren't, buy it or join DAN and read it) when I came upon an incident:
They are claiming that oxidation in the tanks reduced the amount of oxygen available in the tank to less than one percent! That sounds entirely illogical. If the tanks are aluminum, the chance of this is virtually impossible, so I'll assume that they are steel. Even if they are steel and not galvanized (which virturally eliminates rust, especially inside the tank where there is nothing to break the impermeable zinc oxide coating), I still find it almost impossible to believe that this kind of reaction has occurred in a period of say 10-15yrs (even with salt water in the tank) and did not absolutely destroy the tank (ie. BOOM) especially without noticably reducing the pressure. Additionally, it must have been intended as only air (or else any diver would check the O2 in an old tank). Even so, what would someone with the experience that is claimed not check the oxygen content of their tank before using? I have much more chemistry knowledge than the average layman, but there has to be something wrong here. Does anyone have any ideas or more information on this specific case? It also goes to show you how preventable diving accidents are.
brandon
01-63 Instructor without designated buddy
found on wreck; tanks shown to contain
improper gas mix
Cause of Death: Asphyxia
This 42-year-old male was an experienced dive
instructor who worked in a dive shop and
filled his own tanks. He made a wreck dive
with eight other divers but without a designated
buddy to 112 fsw (33.6 msw).
Approximately 35 minutes into the dive,
another diver found the decedent on the wreck
and unconscious. The stricken diver was
brought to the surface and, after some delay,
they managed to get him into the boat.
Resuscitation efforts were unsuccessful. An
evaluation of the dive equipment revealed that
one of the two tanks the decedent had been
using contained less than 1 percent oxygen.
That particular tank contained several ounces
of rust-colored water, and the tank itself had
extensive rust and pitting throughout its inner
surface. The logical conclusion is that this tank
had not been used recently. The oxygen that
was originally present in the tank was likely
consumed in the oxidation (rust) process. The
tank did not have current visual inspection
and hydrostatic testing. Contributing
factor/significant diagnosis included obesity.
They are claiming that oxidation in the tanks reduced the amount of oxygen available in the tank to less than one percent! That sounds entirely illogical. If the tanks are aluminum, the chance of this is virtually impossible, so I'll assume that they are steel. Even if they are steel and not galvanized (which virturally eliminates rust, especially inside the tank where there is nothing to break the impermeable zinc oxide coating), I still find it almost impossible to believe that this kind of reaction has occurred in a period of say 10-15yrs (even with salt water in the tank) and did not absolutely destroy the tank (ie. BOOM) especially without noticably reducing the pressure. Additionally, it must have been intended as only air (or else any diver would check the O2 in an old tank). Even so, what would someone with the experience that is claimed not check the oxygen content of their tank before using? I have much more chemistry knowledge than the average layman, but there has to be something wrong here. Does anyone have any ideas or more information on this specific case? It also goes to show you how preventable diving accidents are.
brandon