On a recent dive trip, on the very last dive of the trip, I noticed my regulator began to breathe hard at the end of the dive. I wrote a message to my dive buddy that it was breathing hard, but since we were right below the boat and I still had over 1000psi left I didn’t worry about it too much. I experimented to see if it breathed harder if I was vertical or horizontal and noticed it would change, but it wasn’t consistently worse in any position. Back on the boat I couldn’t get my regulator off my tank without assistance. I enlisted another diver’s help, thinking my hands were too wet or I was too old and feeble – but he couldn’t get it either. Got the dive guide involved and he was checking to make sure the tank was fully off (it was) and reg was purged (it was). So as one person was purging, the other was loosening the reg off the tank. When it finally came loose, the tank spewed a cloud of white powder that settled like white chalk on the tank and everything around it.
I’ve since learned that the white stuff was aluminum oxide and that this probably happened because a previous diver had breathed the tank down too low, and it got refilled without anyone knowing. Evidently, my reg was breathing hard because the filter in it was doing its job as expected. The dive op cleaned my reg and (I assume) changed out the filter. When it comes to my gear, I’d rather not leave it up to chance, so I’ve already sent it out for servicing.
I’m curious about a couple of things. Why does letting a tank get too low result in this situation?
I have an air analyzer – haven’t used it in a while – but would it have detected this problem? Would aluminum oxide have shown up as a toxic substance in the air?
Someone elsewhere mentioned that if this had happened at depth it could have resulted in a complete out-of-air situation very quickly. Assuming that is true, would I at least experience ONE breath of hard-breathing before going OOA? I’m guessing my lizard brain is now fully alerted for hard-breathing to signal a threat, so I’ll notice subtle changes in how my reg is breathing. Will there be one breath – or is there the possibility I could go OOA without notice if this were to happen in the future?
When refill stations get the tanks back I’m guessing they do NOT check the air pressure before refilling. So how can this be prevented or predicted or … anything?
I’ve since learned that the white stuff was aluminum oxide and that this probably happened because a previous diver had breathed the tank down too low, and it got refilled without anyone knowing. Evidently, my reg was breathing hard because the filter in it was doing its job as expected. The dive op cleaned my reg and (I assume) changed out the filter. When it comes to my gear, I’d rather not leave it up to chance, so I’ve already sent it out for servicing.
I’m curious about a couple of things. Why does letting a tank get too low result in this situation?
I have an air analyzer – haven’t used it in a while – but would it have detected this problem? Would aluminum oxide have shown up as a toxic substance in the air?
Someone elsewhere mentioned that if this had happened at depth it could have resulted in a complete out-of-air situation very quickly. Assuming that is true, would I at least experience ONE breath of hard-breathing before going OOA? I’m guessing my lizard brain is now fully alerted for hard-breathing to signal a threat, so I’ll notice subtle changes in how my reg is breathing. Will there be one breath – or is there the possibility I could go OOA without notice if this were to happen in the future?
When refill stations get the tanks back I’m guessing they do NOT check the air pressure before refilling. So how can this be prevented or predicted or … anything?