Oxygen compatible air and O2 Clean myth

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

CAPTAIN SINBAD

Contributor
Messages
2,997
Reaction score
1,153
Location
Woodbridge VA
# of dives
200 - 499
I have not taken a gas blending course yet but I was reading this article and it confirmed my skepticism of O2 cleaning and O2 compatible air.

Oxygen Clean - Is a Myth • ADVANCED DIVER MAGAZINE • By Bart Bjorkman

Can there be any such thing as oxygen clean anything? Even if we get our deco bottles (that we use for 100%) cleaned for pure O2 and if we get our regulators that we use on them cleaned for pure O2, how long would they stay O2 cleaned realistically? Compressor is not owned by the end user and perhaps someone with dive shop blending experience may enlighten me on this but in the US, most dive shops are blending Grade E. Beyond Grade E the term "oxygen compatible air" tends to lose any agreed upon meaning or a regulated procedure to ensure that it really is OCA.

Lastly, does it matter? By that I mean that if we get our deco regs and oxygen bottles get ahem ..."O2 cleaned," should we really be concerned with contamination that may happen in between those VIP/O2 cleaning years because of "Grade E" air going in and out of those tanks and regs? How common are incidents related to deco tanks and deco regs not being O2 cleaned?

Thanks in advance for your input.
 
I've never had any issues with oxygen, and I O2-clean all equipment myself. If I blend/fill for friends/students, I clean their equipment before filling. Does that give me any guarantees? Maybe not, but this way I have no problem standing next to a tank I'm slowly filling with oxygen.
The 50 liter tanks I use for oxygen, are filled with O2 at the hydro station within minutes, and a Haskel takes care of the last part to 225bar. When ready that tank is too hot to touch, so I usually wait an hour before picking it up.

Most of the time there won't be any issues when you're careful and keep the O2 flowrate low. An exception happened a few years ago: divers were pp-blending their own nitrox in a set of doubles. After minutes, smoke was coming from the manifold. So yes, it can go wrong and it doesn't have to be catastrophic.

OCA: I run the air through an extra filter with MS/AC and finally through a hopcalite filter unit. If that constitutes as OCA? I don't know but I've been breathing that air myself as well. Never had any headaches or other issues, same goes for the divers using air from my bank. I keep track of the hours a filter is used and replace the MS/AC in time.
 
I always assume there’s fuel in the mix somewhere. I keep things cool and work slow with O2, but I do send it through my compressor. You do need to be careful.
 
Chain your cylinders to something to avoid them tipping over and dislodging the valve
That's it for me
 
Divers focus on oxygen clean and oxygen compatible but there is a third element for a piece of equipment to be ready for 'oxygen service.' There is 'oxygen design.' Does the equipment handle the gas gently with slow acting valves and no extreme bends or sudden diameter changes in the gas path?
 
How common are incidents related to deco tanks and deco regs not being O2 cleaned?

They happen, more than a couple boats have burned to the waterline from O2 fires in rebreather tanks/regs.
A technical diving-related burns case: treatment in a remote location

Instead of saying "how common"? Ask yourself: 1) how serious are the possible effects (extremely serious including death as many O2 fires lead to the cylinder exploding) and 2) is there anything simple I can do to avoid this?

Since basically no scuba gear is made with Oxygen in mind (M26 valves are an exception) you have to be more meticulous about the other sides of the fire triangle. Making OCA is crazy easy, air is not the major source of contaminants anyway.
 
I have not taken a gas blending course yet but I was reading this article and it confirmed my skepticism of O2 cleaning and O2 compatible air.

Oxygen Clean - Is a Myth • ADVANCED DIVER MAGAZINE • By Bart Bjorkman

Can there be any such thing as oxygen clean anything?
You can never be 100% certain of anything. But you have to draw a line somewhere. Me, I choose to draw that line at accepted industry practice, because I truly believe that a working industry has found close to the right balance between prudence and workability.

YMMV of course.
 
You can never be 100% certain of anything. But you have to draw a line somewhere. Me, I choose to draw that line at accepted industry practice, because I truly believe that a working industry has found close to the right balance between prudence and workability.
Unfortunately, if you truly, truly follow industry standards (Compressed Gas Association) to the letter, you would pretty much eliminate diving with oxygen at all.

CGA standards require oxygen cleaning for any cylinder containing more than 23.5% oxygen. Scuba normally fills cylinders up to 40% without oxygen service.

Under CGA standards, you cannot use high oxygen mixes with a standard scuba valve, and that is not just because of the speed of opening--it is the path of the gas through the valve. That means that most of the supposed oxygen service scuba valves are still not compliant. Thus, when a scuba cylinder is cleaned and certified for oxygen service (and that includes nitrox service), it is pretty much a lie.

Any idea how hard it is to get hypercleaned air in certain parts of the world? If you want to dive any mix (nitrox or trimix) in much of the world, it will be done through partial pressure blending, and the air used to top it off will be plain old Grade E air.
 
Unfortunately, if you truly, truly follow industry standards
WRT to oxygen-enriched air, there are several standards. Me, I choose to follow the "<40% can be treated like air" standard. If that's wrong and I mess up, I'm perfectly willing to take the consequences of that choice. Because I truly believe that everyone should take the consequences of their own actions.
 
https://www.shearwater.com/products/swift/

Back
Top Bottom