Your Questions about Closed Circuit Rebreather (CCR) diving answered.

[Southside]

I grew up and had an oxy acetylene torch. Played with the oxygen. Learned what that gas can do. I have more respect for the oxygen side of the torch than the acetylene side of the torch. Acetylene may be flammable, Oxygen makes everything flammable. Stuff you don't think would be flammable, like a chunk of steal. The stupid stuff you do when you are young. If someone is good with a torch (I can't do it today) you can start cutting and turn off the fuel. The burning steal is the fuel to keep the cut going. Oxygen does not want to be oxygen by itself.
Static electricity in synthetic materials in a high oxygen environment, no thank you.

Not disputing your point about oxygen being dangerous but acetylene is a very dangerous gas as well. A party balloon or garbage bag full of it can be set off by static electricity and is explosive.

 

[kensuf]

That's kinda one of the reasons why I like the simplicity of the KISS rebreathers which use an off-board dil. Working on the premise that you're carrying an external tank (bailout) anyway, why not use it? I typically dive with a 6 or 8L external tank, which means I'm carrying typically 4-6L (x 200bar) of redundant gas (assuming I might use 2L through my CCR or through inflation). Whilst I may not want to use this for deep exploration diving.... it makes for a very simple setup

Keep in mind that when diving OW while using off-board DIL that is also your bailout, having redundancy is still important. What do you do if your DIL/bailout reg blows a hose?

 

[broncobowsher]

Not disputing your point about oxygen being dangerous but acetylene is a very dangerous gas as well. A party balloon or garbage bag full of it can be set off by static electricity and is explosive.

I have a bottle of acetylene in the garage. I make my own acetylene as well. I'll be doing it in about 2 weeks when I fire off the Calcium Carbide cannon. Acetylene as a pure gas really isn't dangerous. But mix it with air (specifically the oxygen in air) and it wants to burn rapidly. The trash bag/balloon bombs are mixed acetylene, often with pure oxygen since they are taking the gas off a torch. That is pretty much the evil of pumping pure oxygen into a plastic bag full of synthetics (plastics derived from oil, hydrocarbon much like acetylene only a lot more complex of a chain but still one what wants to burn in oxygen).

Mix methane and oxygen and you will get a big ban. Little less than acetylene, but still a big bang. Oxygen and propane will do the same thing. But I can take a huge trash bag of natural gas and light it with a zippo and there is no bang, just a cool mushroom fireball. Yes, I did some stuff as a kid that was rather educational but not the smartest either. There was also the science teacher in junior high that kept a bunch of radioactive stuff in his closet and liked to show us how it behaved.

 

[Gary_Ward]

What do you do if your DIL/bailout reg blows a hose?

Spread my legs and kiss my ass goodbye? I hear ya

 

[Southside]

I have a bottle of acetylene in the garage. I make my own acetylene as well. I'll be doing it in about 2 weeks when I fire off the Calcium Carbide cannon. Acetylene as a pure gas really isn't dangerous. But mix it with air (specifically the oxygen in air) and it wants to burn rapidly. The trash bag/balloon bombs are mixed acetylene, often with pure oxygen since they are taking the gas off a torch. That is pretty much the evil of pumping pure oxygen into a plastic bag full of synthetics (plastics derived from oil, hydrocarbon much like acetylene only a lot more complex of a chain but still one what wants to burn in oxygen).

Mix methane and oxygen and you will get a big ban. Little less than acetylene, but still a big bang. Oxygen and propane will do the same thing. But I can take a huge trash bag of natural gas and light it with a zippo and there is no bang, just a cool mushroom fireball. Yes, I did some stuff as a kid that was rather educational but not the smartest either. There was also the science teacher in junior high that kept a bunch of radioactive stuff in his closet and liked to show us how it behaved.

Now that you say that, I remember a welding instructor putting a torch up to a lit cigarette and turning the oxygen on. It was gone in about 2 seconds.

I have also heard stories of welders using oxygen to blow debris off their coveralls and then lighting a cigarette.... I have no direct knowledge of that happening and am not sure if it's just one of those stories, but I know it has the potential to happen.

 

[Barmaglot]

Would it make sense to consider using argon for suit inflation an extra safety factor when using potentially flammable heated undergarments?

 

[broncobowsher]

Unless you are running elevated oxygen levels there is nothing to worry about. The oxygen levels in air are not elevated enough to be an issue.

 

[Derick P]

Great video and great discussion. After taking a 20 year hiatus from diving I’m looking at getting back into the sport. When I was in the Marine Corps, our combat divers used the Draeger rebreathers. So cool to see that tech available now in the civilian market.

 

[rjack321]

In this case, a claim was made that a rich mix for suit gas wasn't a problem, because in the personal experience of the poster, it hadn't been a problem in 20 years (although he never uses heat). That's the very definition of normalization of deviance. Three other posters then offered examples of horrible accidents caused by this practice (which wouldn't have made it into a fatality database).

This is not normalization of deviance. People adding heat and having incidents because of that is a completely different concept. You have to start somewhere and doing new things that have no knowledge base behind them and getting surprised by the pitfalls is just lack of knowledge. If we didnt change or add new ideas to the pool of knowledge we would still be using steel 72s, frenzy BCs and J valves

 

[doctormike]

This is not normalization of deviance. People adding heat and having incidents because of that is a completely different concept. You have to start somewhere and doing new things that have no knowledge base behind them and getting surprised by the pitfalls is just lack of knowledge. If we didnt change or add new ideas to the pool of knowledge we would still be using steel 72s, frenzy BCs and J valves

Disagree, but mainly just a semantic thing.

Saying that you have been doing something for 20 years without incident, especially a senior person saying that in a public form, has implications for new divers, who may take home the message that it's safe.