Prevalence, causes, and prevention of oxygen fires

[rjack321]

#7 is interesting. Medical O2 uses BUNA-N O-rings according to The OxyHacker book. We use Viton. So it's not clear what O-rings are worse for O2 service until you get into less common compounds. Our valve seats are almost uniformly nylon or nylon compounds that are not used elsewhere for O2 service as far as I know, and not truly best for it, either. Moreover, the gas path through most valves used in diving could be, um, better for O2 service. The HP hoses have very little flow unless a spool O-ring blows (and even then it's restricted by the regulator design in most cases), and the LP hoses are, well, LP and don't impose that much risk as far as I can recall. (If anyone knows better please chime in.)

With all that in mind, that we have so few accidents with O2 is slightly astonishing. Not just O2 fires but gas contamination.

Wut he said ^^^ Surprised we don't have more problems given the equipment we start with.

Most scuba valves and regulators were never designed for oxygen service in the first place. The "Best practice" would be to start with properly designed valves that open slowly, that don't have sharp bends in the flow path and don't use nylon seats. They would feed regulators which don't have tortuous flow paths, don't use as many combustibles in the first place, etc

 

[lowviz]

...//... But it shouldn't be necessary. If the equipment is clean and properly designed, opening the valve quickly should have no effect.

Maybe.

I tend to see oxygen as no big deal to handle and a huge benefit to have on hand.

I do have serious doubts about rapidly pressurizing valves and hoses, though. Maybe picked that caution up at work or maybe it came from here:

 

[Marie13]

Another SB poster posted a while back about a diver who had a deco bottle explode underwater, suffering burned throat/respiratory system (??) and ended up dying from his injuries, if I remember correctly.

 

[2airishuman]

That would be @rhwestfall. One of the many secondhand reports.

 

[rhwestfall]

Yes, my instructor's buddy...

 

[Schwob]

One point that I think is worthy of discussion and analysis is: are DIN valves appropriate for high concentrations of O2? The ridged nature of the DIN threading provides many times more potential combustion sites in the event of an accidental opening of the valve. Is it safer to always store O2 cylinders with DIN valves with a regulator attached?

Curious about that. What do you mean? What ridges are in the path of O2 flow that would not be in it's path with a yoke valve?

That said, slow opening valves, non tortuous paths, seats out of less combustible material than nylon (yet ansolutely non sparking) and maybe regulator/valve unibodies...

@2airishuman : Why is it that a unibody valve regulator might be better (safer) in itself if not also slow opening, non tortuous path, etc.?

Very interestin thread topic BTW.

 

[JohnnyC]

I think a large part of it is that we, as scuba divers, have comparatively little experience with pure O2, and even less, see the consequences of mishandling.

As an example, in the welding and fabrication world, everybody knows how to use an oxy fuel torch and it is drilled into everyone the proper procedure for handling and use. I would posit there are MORE accidents in an industrial setting, but probably an order of magnitude or more O2 use.

 

[RainPilot]

I've never really understood why removable 1st stages are used for deco bottles (other than tradition).

If you have an IP creep or something happen to the 1st, your whole deco bottle is gone until it can be serviced. This will probably cancel your dive day depending on logistics available. A quick 1st stage swap with a spare from your bag is a lot easier.

I love the idea of those integrated valve/regs especially for bailout but its just not practical for me.

 

[J-Vo]

...I personally think it should be inserted in to OW & TECH courses, ...

Why for OW when they should be using air?

I would say my basic Nitrox course was over the top on O2 safety considering it only certified me to <40%.

All of my tech training has had large portions of the text dedicated to O2 handling and safety.

Don't even get me started on my blender course.

 

[JackOfDiamonds]

Why for OW when they should be using air?

I would say my basic Nitrox course was over the top on O2 safety considering it only certified me to <40%.

All of my tech training has had large portions of the text dedicated to O2 handling and safety.

Don't even get me started on my blender course.

Maybe AOW will be more appropriate considering they will be using nitrox, how ever you should start this learning process from the very start so it settles in your mind.
Even OW divers still sometimes hang around tanks filled with oxygen so teaching them the proper safety in my opinion is vital.

As in regards to the tech diving, having not done one myself i cannot say for sure what they teach you and what they dont teach you, this is based on my observations of divers in my area who are tech certified and have very little to no extended knowledge on the safety and handling of oxygen rich tanks.

To be honest, ive seen Tech Divers who are less capable in the water then some AOW divers i know, i guess it all depends on the organization that you take the course with and the instructor . (And at the end of the day, incompetent people will always be incompetent.)

Sorry for my ignorance but i have no idea what a Blender course is, care to share please?