Two divers critical - Hawaii

[Superlyte27]

Are you certed on any rebreather?

I’m guessing not. It’s painful to have these discussions with someone who just doesn’t get it because they have no experience.

Gah! I’ll do it anyway...
Wet rebreather sitting in the back of your car doesn’t have enough oxygen to sustain life because you don’t want to be cooking your sensors. You see, galvanic oxygen sensors are like a fuel cell. Oxygen is burning up the fuel. That reaction gives off an electrical charge, that charge is read by a computer which tells PPO2. Yes, I’m sure you know all of this. But, why have those cells cooking in oxygen when not needed, like a car ride home. So, we void the oxygen and just put air in the loop. .21ppo2.

 

[fuzzybabybunny]

This isn't even getting into the entire plethora of ways the programmers of the unit can change the unit's behavior and provide customization for you, the diver, without adding or changing any hardware.

Don't want it to sound an alarm when it detects PO2 drop but it's in less than 1.5 meters of water? Fine. Turn that feature off when you're setting up your unit. You're losing absolutely nothing. But it certainly sounds like you could still drown in 5 feet of water if you become unconscious due to PO2 drop considering you sink if your counterlungs flood.

Don't want audible alarms for anything? Fine. Turn them all off. Or turn only some off. Do whatever. You're not losing anything and the programming logic resides in the chip of the computer anyway so nothing mechanical is changing.

 

[Superlyte27]

This isn't stuff that requires a hardware fix or a hardware addition. This is a programming issue.

You’re right. It is a programming issue. Program your brain to turn on your oxygen and computers. The two leading causes of CCR fatalities.

If you know you can’t be diligent in doing that, stay away from CCR.

Dear God Man!!!
Four visual alarms and you really think more is going to change anything?
Ever seen a crash with a backup alarm on a moving truck? I recently witnessed a pedestrian get mowed over by a truck that was beeping for 45 seconds while it backed over a person who was enamored with her cell phone text. She never looked away from her phone until she was under the truck. This isn’t an engineering issue. It’s a complacency issue. I hate to speak ill of the dead, but you can’t fix stupid. YOUR LIFE IS MORE IMPORTANT THAN A CAMERA.... or texting.

 

[Superlyte27]

What rebreather are you certified on?

 

[doctormike]

That's exactly what I'm asking.

Why don't audible alarms sound when the unit is wet and above 1.5 meters?

Why doesn't it start monitoring the drop in PO2 when the unit is wet and above 1.5 meters?

It's obvious the unit's not at a picnic table anymore if it's wet and submerged in any amount of water. Even on a surface swim the PO2 should be monitored and alarms sounded, no?

If you get into a car and the handbrake is on the car doesn't start yelling at you only after you've reached a speed above 15 mph - it starts yelling at you the moment it gets put into drive, while the car is stationary and before your foot is even on the gas pedal.

Hi, Fuzzy…

I get where you are coming from. And your basic premise is not wrong - for very complex systems that people’s lives depend on, there should be fail-safes built in that prevent common operator errors from becoming fatal.

Rebreather manufacturers believe this too, and there are many engineering solutions implemented along theses lines in most units. Some rebreathers have lots of these (like the Liberty), and some have less (like the JJ). And it’s not as if the more the better - not everyone wants to get the model that has the most complex backup systems. Many CCR divers prefer rebreathers that are simple and robust - each of these clever fixes introduces their own failure modes and usability tradeoffs. The market is pretty good at deciding where to draw that line between being overly simple and overly complex.

But at some point, you really have to rely on training, situational awareness and compulsive attention to standardized protocols on the part of the operator. From the outside, it’s tempting to say that even one fatality is unacceptable and the cause needs to be engineered out of existence. But it just doesn’t work like that. There are so many things that a CCR diver needs to be able to deal with that you will never make a unit that can fly itself and keep the operator safe.

So Superlyte27 basically just said what I was getting around to saying in a much wordier post. Put a 10 cent checklist sticker on your handpiece, and EVERY TIME you are in your rebreather and about to splash, run down the checklist: Turn on your valves, check your SPGs, check your MAV and ADV, turn on your handset and HUD, prebreathe the unit for 5 minutes and watch it hold your set point, check your wing, drysuit and bailout. Then jump in the water.

 

[fuzzybabybunny]

Are you certed on any rebreather?

I’m guessing not. It’s painful to have these discussions with someone who just doesn’t get it because they have no experience.

Gah! I’ll do it anyway...
Wet rebreather sitting in the back of your car doesn’t have enough oxygen to sustain life because you don’t want to be cooking your sensors. You see, galvanic oxygen sensors are like a fuel cell. Oxygen is burning up the fuel. That reaction gives off an electrical charge, that charge is read by a computer which tells PPO2. Yes, I’m sure you know all of this. But, why have those cells cooking in oxygen when not needed, like a car ride home. So, we void the oxygen and just put air in the loop. .21ppo2.

I'm guessing you're not a trained programmer? Or an engineer? Trust me the pain in this conversation is mutual.

We both have the same goal in that we don't want to see anyone die. Only difference is one of us chooses to just blame people instead of entertaining the thought that maybe, just maybe, we can engineer a better system. Maybe we can prevent scenarios like this from happening through improved product engineering while at the same time NOT have your precious oxygen sensors burn up because your unit's a little wet in the trunk of your car. Maybe these two goals aren't mutually exclusive.

 

[wgw04024]

I apologize if there is an obvious answer to this, but I'll take the risk. Why can't the CCR release oxygen to keep the ppo2 in the loop at a survivable level 'before' it goes into 'dive mode'? Is it possibly because if the CCR is on but the loop isn't in the divers mouth it will 'waste' the o2?

Thanks.

 

[doctormike]

I apologize if there is an obvious answer to this, but I'll take the risk. Why can't the CCR release oxygen to keep the ppo2 in the loop at a survivable level 'before' it goes into 'dive mode'? Is it possibly because if the CCR is on but the loop isn't in the divers mouth it will 'waste' the o2?

Thanks.

It can and it does. The Liberty in surface mode "is designed to maintain a pre-set oxygen volume of 23% by adding oxygen if the O2 sensors detect a drop below this amount. This addition of oxygen functions automatically and is intended as a safety feature to prevent depletion of oxygen from the loop while the unit is running unintentionally in surface mode." (from the official Divesoft report cited above)

But it can't do that if the O2 is turned off.

 

[Superlyte27]

Nope, not an engineer or programmer. The frustrating part is that you think this stuff can be engineered or programmed. It can’t. Just like you can’t fix the rare chance that a plane will fall out of the sky. I’d guess that happens about half as much as rebreather deaths at about 1 death per 100k hours. It’s higher for private pilots than commercial pilots. But just like you can’t make a plane that is accident proof, you can’t make a rebreather that is fool proof. And I love that I get to use the word “fool” in that proof. Because if you don’t take these things seriously, you are a fool.

Look, no one is forcing you to take this vastly more complicated piece of equipment diving. But if you do, there are certain things that must happen. Just like I said about cave diving. I am 100% certain that if I follow all 5 rules of cave diving I will live 100% of the time. I am also certain that if I do the handful of checks that I should do on the CCR, it won’t kill me. If you’re not willing to do your due diligence, no amount of engineering or programming will save you on a CCR. I promise. In fact, I’ll give you a rebreather class. Pick Optima or Liberty. Come to Florida for a week. I’ll lend you the unit, give you all of the instruction. At the end of it, tell me that you can engineer away stupidity or complancency. Convince me of that, and you can have the rebreather you train on.

 

[wgw04024]

I think I just read my answer in Divermike's post. Breath the loop for 5 minutes to make sure it holds the setpoint. So the alarm just doesn't sound above 1.5m depth.