Filmmaker Rob Stewart dies off Alligator Reef

[The Chairman]

I've never been so fatigued that I just let my loop fall out of my mouth

When I get fatigued, I make mistakes. Many of them simple, simple mistakes. See a friend and mentor stumble and I can see this happening easily. Hell, I've made that mistake on both a Revo and an SF2 and I wasn't even fatigued.

 

[Dan]

All it takes to understand this is a high-school level understanding of chemistry. It's a four step process that goes thus:

1: CO2 + H2O --> H2CO3
2: H2CO3 + 2 NaOH --> Na2CO3 + 2 H2O + Energy
3: Na2CO3 + Ca(OH)2 --> CaCO3 + 2 NaOH

4: Meanwhile, CO sees all this math and runs, screaming, from the classroom. Thereby CO is eliminated from the breathing gas.

And it's not an absorption, nor adsorption. It's a reaction. I also can't recall any possible reaction of CO with NaOH or Ca(OH)2 in my college chemistry.

 

[The Chairman]

I might very well have been taught wrong. I've actually sent an email to Molecular Products to verify just that. One of the best things about a forum is that misconceptions can actually die.

 

[St John the Diver]

I might very well have been taught wrong. I've actually sent an email to Molecular Products to verify just that. One of the best things about a forum is that misconceptions can actually die.

You were.

That's basic chemistry.

 

[Neuatomic]

Hopcalite?

 

[eelnoraa]

All it takes to understand this is a high-school level understanding of chemistry. It's a four step process that goes thus:

1: CO2 + H2O --> H2CO3
2: H2CO3 + 2 NaOH --> Na2CO3 + 2 H2O + Energy
3: Na2CO3 + Ca(OH)2 --> CaCO3 + 2 NaOH

4: Meanwhile, CO sees all this math and runs, screaming, from the classroom. Thereby CO is eliminated from the breathing gas.

A balanced chemical equation is just equating masses, it is by no mean the reaction will necessary happen. Amougst these, #3 is not going to happens. #1 can theoriotically happen, but this reaction is so weak, you really don't get any H2CO3 ( low reaction rate, low H+ concentration, extremely weak acid). NaOH is a strong base,#2 can happen, but what really happen is you dilute the NaOH with water. Probably should revisit high school chemistry

 

[Capt Jim Wyatt]

Hopcalite?

Yes.

We have hopcalite in air compressor filters and it will remove/catalyze small amounts of CO when temps are below 120F in the stack.

 

[oya]

When I get fatigued, I make mistakes. Many of them simple, simple mistakes. See a friend and mentor stumble and I can see this happening easily. Hell, I've made that mistake on both a Revo and an SF2 and I wasn't even fatigued.

Do you also sometimes forget to breathe?

There are mistakes and there are mistakes.

Pete, seriously and without meaning to sound snarky (which I know it will over the Internet no matter that I don't mean it with snark), if you are letting the DSV drop out of your mouth accidentally perhaps you shouldn't be diving a rebreather.

A balanced chemical equation is just equating masses, it is by no mean the reaction will necessary happen. Amougst these, #3 is not going to happens. #1 can theoriotically happen, but this reaction is so weak, you really don't get any H2CO3 ( low reaction rate, low H+ concentration, extremely weak acid). NaOH is a strong base,#2 can happen, but what really happen is you dilute the NaOH with water. Probably should revisit high school chemistry

Probably you should get in touch with Intersurgical and Molecular Products and alert them that all their chemists are wrong. I didn't write those equations, they did.

 

[The Chairman]

@oya,

seriously, until it becomes an ingrained habit, it's quite easy to allow your DSV to leave your mouth without turning it off. That's the entire point of training: to create great habits. That's also the point of gaining experience before you take another step like trimix or hypoxic trimix. We don't know how many hours he had on a rEvo. Rumor has it that this was a borrowed unit and not even his own, so he probably didn't have that many hours. It's why many of us believe that he went too far, too fast.

Now, if you're telling me that anyone who makes any mistakes ever on their rebreather should not be diving on one, then I'm going to cry "hypocrite" and ask you to stop diving yours. Unless, of course, you're claiming to have never ever made a mistake on your rebreather and are also suggesting that fatigue can not be a factor in making simple mistakes. That's the depth of foolishness to not make allowances as your limits, cognitive and otherwise, are compromised by any number of factors including cold, depth, distractions and yes, even fatigue. Just because a dive can be done on paper, doesn't mean it should be attempted. Ask Doc Deep, oh wait: he died too. A diver's got to know and honor their limitations. I'm a very cautious diver and I credit that cautiousness to having never been bent or injured on a dive going on now 48 years since first breathing underwater. It's not from having never made a mistake either. Humans stop making mistakes right when they die. For me it's been a matter of good training with a lot of experience thrown in to make that training useful. A good diver makes very few mistakes. A great diver knows how to identify and rectify each and every one before it becomes an incident.

 

[St John the Diver]

@oya,

seriously, until it becomes an ingrained habit, it's quite easy to allow your DSV to leave your mouth without turning it off. That's the entire point of training: to create great habits. That's also the point of gaining experience before you take another step like trimix or hypoxic trimix. We don't know how many hours he had on a rEvo. Rumor has it that this was a borrowed unit and not even his own, so he probably didn't have that many hours. It's why many of us believe that he went too far, too fast.

Now, if you're telling me that anyone who makes any mistakes ever on their rebreather should not be diving on one, then I'm going to cry "hypocrite" and ask you to stop diving yours. Unless, of course, you're claiming to have never ever made a mistake on your rebreather and are also suggesting that fatigue can not be a factor in making simple mistakes. That's the depth of foolishness to not make allowances as your limits, cognitive and otherwise, are compromised by any number of factors including cold, depth, distractions and yes, even fatigue. Just because a dive can be done on paper, doesn't mean it should be attempted. Ask Doc Deep, oh wait: he died too. A diver's got to know and honor their limitations. I'm a very cautious diver and I credit that cautiousness to having never been bent or injured on a dive going on now 48 years since first breathing underwater. It's not from having never made a mistake either. Humans stop making mistakes right when they die. For me it's been a matter of good training with a lot of experience thrown in to make that training useful. A good diver makes very few mistakes. A great diver knows how to identify and rectify each and every one before it becomes an incident.

I have never had a student get thru rebreather training without dropping the loop at least once.

"Experience is the name we give to survivable errors".

With that said, the possibility of loss of buoyancy on the surface is something that I hammer and hammer and hammer into my students.