Wouldn't be on a hypoxic mix then.
Regular quarry diver found dead - Falling Rock Park, Kentucky
- Thread starter DandyDon
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Wouldn't be on a hypoxic mix then.
Rooster59
Contributor
There's a hole a bit east of the middle, seems like a 2nd thermocline and about 70' deep or so.
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the reporting isn't clear if the rebreather was a mixed gas rebreather (which has a diluent)
or an oxygen rebreather which has no diluent.
The former could be hypoxic and result in him passing out.
Its hard to make an oxygen rebreather hypoxic unless you pump it full of ambient air before descending. Once you are at depth its impossible to make it hypoxic.
Then again at 62yo (although it can happen at any age) he could have had a heart attack or stroke and the rebreather is a completely irrelevant detail.
or an oxygen rebreather which has no diluent.
The former could be hypoxic and result in him passing out.
Its hard to make an oxygen rebreather hypoxic unless you pump it full of ambient air before descending. Once you are at depth its impossible to make it hypoxic.
Then again at 62yo (although it can happen at any age) he could have had a heart attack or stroke and the rebreather is a completely irrelevant detail.
Obviously I know nothing about what happened other than what was in that article, but the point of this forum is to consider "what-ifs"... and of course, there are lots of things that can kill a person other than a rebreather problem. For example, a survivable heart attack at depth is likely to be fatal underwater.
But for the purposes of this discussion, and for the non-CCR divers: there are three main problems that can be lethal with a closed circuit rebreather - hyperoxia (high PO2), hypoxia (low PO2) and hypercapnea (excessive CO2).
Hypercapnea comes from either producing CO2 faster than the scrubber can clear it due to overwork, or a bypass of the scrubber due to a problem with the one-way valves or the scrubber itself. I kind of doubt that would be an issue in 19 feet of water, probably would have resulted in panic and surfacing, if anything.
Hyperoxia is not possible in 19 feet of water, even with a pure O2 rebreather (as mentioned upthread, but very rarely seen in the wild), you can't get your PO2 to toxic levels in the short term at that depth.
Hypoxia is frequently the cause of shallow water death on CCR, since the first symptom may be loss of consciousness. And if for any reason your CCR is not adding O2 to the loop, you will quickly drop your PO2 down below levels that will support consciousness (and life). This has happened many times, read the first three stories on my checklist sticker blog entry. Some dive boats will ask each diver for their PO2 before splashing, one local captain told me about a crew member who stood up from his seat amidships while on the loop, walked towards the stern and passed out before making it to the dive deck.
Sorry, I think that I see your point - didn't mean to seem snarky.
But I think that it's important to stress that you don't need hypoxic dil to rapidly drop the loop PO2 to unsafe levels. You would be at risk with a hypoxic dil flush, of course, but if you aren't getting O2, then any mix becomes hypoxic quickly.
Very sad event. I have dived may times at FRP although don't dive there often.
My reading of the media report above in says that the victim built a "home brew rebreather" but doesn't indicate that is what he was diving at the time of the incident.
I associate "shallow water hypoxia" with breath-hold or free diving in which divers hyperventilate "blowing off" enough Co2 to allow them to resist the urge to breathe to the point of passing out after having metabolized the available oxygen. These divers usually pass out during the ascent near the surface when the PPO2 is dropping - hence the "shallow water" moniker.
If Mr. Price were diving a rebreather it seems to me that this accident may be attributable to hypoxia due to failure of o2 sensor(s). Can't say how many (if any) redundant O2 sensors were in place in a "homebrew" rebreather.
If his "homebrew rebreather" was an oxygen rebreather, he could have suffered oxygen toxicity due to diving to unsafe depths (even 40' on pure O2 is a PPO2 of over 2ATA and would be unsafe). Hypoxia seems less likely a scenario as an O2 rebreather uses only O2 in the loop and therefore consuming the o2 in the loop would reduce the volume in the loop which I would expect to alert the diver to a problem before becoming hypoxic.
If it were not an oxygen rebreather, hypoxia seems more possible to me as an o2 sensor failure and consuming the o2 in the diluent would likely result in hypoxia.
Condolences to the family.
My reading of the media report above in says that the victim built a "home brew rebreather" but doesn't indicate that is what he was diving at the time of the incident.
I associate "shallow water hypoxia" with breath-hold or free diving in which divers hyperventilate "blowing off" enough Co2 to allow them to resist the urge to breathe to the point of passing out after having metabolized the available oxygen. These divers usually pass out during the ascent near the surface when the PPO2 is dropping - hence the "shallow water" moniker.
If Mr. Price were diving a rebreather it seems to me that this accident may be attributable to hypoxia due to failure of o2 sensor(s). Can't say how many (if any) redundant O2 sensors were in place in a "homebrew" rebreather.
If his "homebrew rebreather" was an oxygen rebreather, he could have suffered oxygen toxicity due to diving to unsafe depths (even 40' on pure O2 is a PPO2 of over 2ATA and would be unsafe). Hypoxia seems less likely a scenario as an O2 rebreather uses only O2 in the loop and therefore consuming the o2 in the loop would reduce the volume in the loop which I would expect to alert the diver to a problem before becoming hypoxic.
If it were not an oxygen rebreather, hypoxia seems more possible to me as an o2 sensor failure and consuming the o2 in the diluent would likely result in hypoxia.
Condolences to the family.
fsardone
Solo Diver
Not really. My father used to dive O2 rebreather to 20 mt (60+ ft) it was 1950s many things were unknown but the trick was not flushing well to keep the PO2 low. Due to the way the O2 CCR works, it only add gas when the volume goes to below a normal breath (is a demand valve like a second stage) so there is achance to metabolize most of the oxygen but still have enough Nitrogen not to trigger the valve, guess that is what you meant by pump it full of ambient air.
Fact is when you are deep (not below 6 mt ) you might have enough oxygen to keep you awake but raising up just few meters or using up the 21% you have in the bag if you did not flush will leave you unconscious.
Not sure you have a training course for a self built ... and you might not have all the details if you are a self tought pure O2 CCR diver.
Offence not taken: I'm from the Usenet.
You are right though: I was thinking the "normal" scenario of using a hypoxic mix at depth and coming up faster that the system adjusts (for whatever reason) -- did not consider O2 sensor failure nor what @fsardone describes. (PS. I did phrase it rather carefully though.)
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