Rebreather Diver dies in Pool in Oregon

[wedivebc]

I'd be interested to hear why rebreathers are still being sold that allow a user to continue breathing a mix that will not support life.

The formulas are known and all the other variables can be measured (depth, current o2%, co2% n%, etc.), which means that the ability of a mix to support life at any particular depth can be calculated.

Why would a manufacturer build equipment that is essentially a death machine?

Continuing to breathe a mix that can no longer support life deserves some action from the rebreather that would prevent this, such as dumping all the gas from the loop or closing it off when it can no longer support life.

Terry

I understand what you are getting at but lets be practical. It is like asking why do they still sell cars that can crash. Like most things in life. the user has to be responsible for the outcome of the operation.
You would no more want a scuba set that dives for you than a rebreather diver does. Gee, many people even reject carrying a computer to caculate deco so why would someone entrust their entire life to a piece of electronic hardware? I am not sure why you think monitoring depth, current and n2% are important and current technology is moving toward co2 monitoring so we're getting there.
I am sorry this fellow had to die and I respect the need for diplomacy and sensitivity but also these forums do give us a place to analyze information and learn from others mistakes so we don't have to repeat them. This may incedent may draw some (well deserved) critical attention to training methods. I for one support omars right to post what he did even if I would have used a little more tact myself.

 

[Al Mialkovsky]

Hey those things are expensive enough. Let's not build one that's bullet proof. What the heck would that end up costing?

 

[JonnyB]

I don't dive a rebreather yet, and it's very likely that my guess could be wrong. However, if a scrubber goes past it's usefull limit, and starts a slow build up of CO2, would you still see it coming and experience the buildup of CO2 as rapid? (honestly asking a question here) Or am I out to lunch on how a scrubber failure due to overuse would manifest itself?

Hi, i will try to explain the effects of hypercapnia to you by telling you about an experiment i did last year.
I wanted to get first hand experience on hypercapnia, CO2 buildup. So what i did was to remove all sofnolime from my scrubber, i dive a Classic KISS at that time. I put the whole unit together, say my *** on the floor, had a friend watch over me as i started to breath on my unit with out any absorbent. Well it did not take long before i could start to feel all the symptoms described in the text books... I was not able to stay on my RB for more than a minute. I felt like anxiety, heavy breathing, dissorientation, i may also add that by the end i just wanted to die... Not a very pleasant feeling. I had the worst headache of my life. Straight after the experiement i started breathing pure O2 just to clean my system from the CO2, but the headache was there all day. I am not doing it again, ever... but i am glad i did cause now i do have an idea what it is all about, i do change my scrubber in time and i never want to experience this underwater, that is for sure.

So CO2 does not creep up on you the same way hypoxia does

hope this gives you an idea
kind regards
Jonny

 

[bradshsi]

What I found strange about the incident was this part of the events as told in The Columbian story:

"McGinnis said Harris was an occasional customer who had gone diving the day before in the Tacoma area. On Monday, he stopped by Thunder Reef to get his gas cylinder refilled.

Harris was waiting for a Thunder Reef employee who is a trained gas blender to return to the store, McGinnis said. Since Harris still had some gases in his cylinder, he decided to use it up with his rebreather in the shop's pool for practice.

Harris was alone in the pool, which Thunder Reef allows in the case of highly experienced divers, McGinnis said."

Assuming the above to be true. If the diver was purposesly trying to breath down his (near empty) cylinder, why would he not monitor the cylinder pressure very carefully and exit the water before it was completely empty ?

 

[Web Monkey]

I understand what you are getting at but lets be practical. It is like asking why do they still sell cars that can crash.

It's nothing like that at all.

It's more like the reason your airbag deploys when your car senses that you're about to smash your head into the steering wheel. It's a final effort by the equipment to try to prevent your death.

Like most things in life. the user has to be responsible for the outcome of the operation.

You would no more want a scuba set that dives for you than a rebreather diver does.

I don't want it "diving for me", however since there are various breathing gas mixes that will not support life, and it's easy to monitor with inexpensive hardware, there's no reason to not do it.

It's not like any sane person would choose to dive with a mix that can be predicted to cause death.

Gee, many people even reject carrying a computer to caculate deco so why would someone entrust their entire life to a piece of electronic hardware? I am not sure why you think monitoring depth, current and n2% are important and current technology is moving toward co2 monitoring so we're getting there.

I was referring to depth, current % of O, N and CO2, not current as in the direction the water is moving.

My point is that it's easy to monitor all the major components of the mix using inexpensive electronics, and to take automatic decisive action when the mix will not support life.

Terry

 

[Web Monkey]

Hey those things are expensive enough. Let's not build one that's bullet proof. What the heck would that end up costing?

For a couple of sensors, a small PC board and a valve? Maybe another $500 - $1000?

Terry

 

[bradshsi]

For a couple of sensors, a small PC board and a valve? Maybe another $500 - $1000?

Terry

With all due respect, I don't agree with that analysis.

As an engineer I've worked with instrumentation and control valves many times. What you quickly learn is that more sensors/valves = lower reliability (It's a simple calculation to determine the total serial reliability of a system).

Gas sensors in particular are not very robust. They need periodic calibration (say before each dive). Even allowing for that they can fail during the dive with potentially fatal results.

The only way improve the overall system reliability is to have less components to fail (a simpler system) or have a parallel reliabilty system (meaning 2 or 3 sensors with a voting system or secondary readout).

With parallel sensors and systems, the task loading and training requirement for the diver increases. This in turn can lead to additional accidents when the operator fails to operate the system in the correct sequence.

In summary I don't agree that more electronics is necessarily a "cure all".

 

[Web Monkey]

People are dying, and from the number that apparently fall asleep or pass out, it's clear that some additional or different technology is needed.

Sensors are available that would prevent this, and even if it added another $3K to the cost of a rebreather, it would seem to be worth it. I know my life is worth more than $3000.

Terry

With all due respect, I don't agree with that analysis.

As an engineer I've worked with instrumentation and control valves many times. What you quickly learn is that more sensors/valves = lower reliability (It's a simple calculation to determine the total serial reliability of a system).

Gas sensors in particular are not very robust. They need periodic calibration (say before each dive). Even allowing for that they can fail during the dive with potentially fatal results.

The only way improve the overall system reliability is to have less components to fail (a simpler system) or have a parallel reliabilty system (meaning 2 or 3 sensors with a voting system or secondary readout).

With parallel sensors and systems, the task loading and training requirement for the diver increases. This in turn can lead to additional accidents when the operator fails to operate the system in the correct sequence.

In summary I don't agree that more electronics is necessarily a "cure all".

 

[Mr.X]

People are dying, and from the number that apparently fall asleep or pass out, it's clear that some additional or different technology is needed.

Sensors are available that would prevent this, and even if it added another $3K to the cost of a rebreather, it would seem to be worth it. I know my life is worth more than $3000.

Terry

Pools are deceptive. They seem benign and complacency can set in. When I set up in a pool I always have someone look after me - regardless. I know in some drowing/near drowning cases that the diluent mix was way too lean to start, or oxygen not turned on. Following pre-dive protocols regardless of depth + a topside buddy would be the monitoring system needed.

BTW...Like your shots of the Keystorm + Moe and Khris's boat!!!

 

[Mverick]

People are dying, and from the number that apparently fall asleep or pass out, it's clear that some additional or different technology is needed.

Sensors are available that would prevent this, and even if it added another $3K to the cost of a rebreather, it would seem to be worth it. I know my life is worth more than $3000.

Terry

If it was easy to do, or even difficult to do. And reliable. It would already be done. CO2 sensors aren't reliable YET in RB applications...

APD actually uses a Temp stick. For the scrubber stack. Because, CO2 sensors weren't reliable yet. But, the Temp stick won't catch a break through from a bad scrubber pack job. It measures the heat front running through the scrubber. NOT CO2.

It's easy to say we need it. It's difficult trying to get them to work. If all the tech stuff was already here. It would be on a unit already. I know of others coming to market. And stated they have way's to measure CO2. Yet when pressed. They aren't measuring CO2. They are estimating based on other assumptions. I'd rather not have it then have one that MIGHT work... Sometimes....

Just wondering. Do you dive RB's? Or have any experience with them. Not being a smart a^% Just wondering. I've built my own and dive one that is Built by someone else all the time.