Is 2%Ar OK in 35% Nitrox?

[Lobzilla]

I am considering to add an Oxygen concentrator to my liveaboard filling system. The Pressure Swing Adsorption Method (PSA) used in medical and industrial Oxygen concentrators removes Nitrogen from the air and thereby not only increases the Oxygen content but also the Argon content at the same rate.

36% Nitrox produced using PSA would have no more than 2% Argon in it.
Is that acceptable as far as the narcotic and DCS inducing effects of Argon are concerned?

This unit would also produce 95%O₂ with ~5%Ar. Is that OK for pre and post dive surface use?

Related thread in compressor forum is here


PS: How does one fix a typo in the thread subject?

 

[Dr Deco]

Hello Lobzilla:

I would suspect that the small increment of argon would not be problem with a large addition of oxygen. Recall, however, that diving and argon has not been investigated in humans since it is really a bad diving gas.

Dr Deco :doctor:

 

[miketsp]

Purely an engineer's personal opinion - for what it's worth.
As a common gas in the atmosphere you're already breathing 0.93% so 2% is not much more.
Although considered one of the 5 inert gases it can produce some compounds but nothing that should be significant.
It's considered non-toxic actually being used in various food processes.
It's colourless, odourless and tasteless so shouldn't provoke any nausea.

It has also used experimentally to replace nitrogen in the breathing or decompression mix, to speed the elimination of dissolved nitrogen from the blood. Argox.
Pilmanis Andrew A, Balldin UI, Webb James T, Krause KM (December 2003). "Staged decompression to 3.5 psi using argon-oxygen and 100% oxygen breathing mixtures". Aviation, Space, Environmental Medicine 74 (12): 1243–50.

http://www.ncbi.nlm.nih.gov/pubmed/14692466


However Argon, does have 2.33 times the narcotic effect of nitrogen but if you're using it in rich O2 mixtures you're not going very deep anyway.

I wouldn't have any qualms at the % you're talking about.

 

[PfcAJ]

I would not dive on a boat that had 95% oxygen as their emergency surface DCS treatment gas, nor would I buy gas from a source with 2% argon. There are other methods that do not have these drawbacks.

 

[lowviz]

Argon is a common welding gas. Inert and nontoxic, but can't support life. It is 2.3 times more narcotic than nitrogen -as miketsp noted (International textbook of Mixed Gas Diving H.K.J. Lettnin 2001), thus as Dr. Deco said, a bad diving gas. For EAN 36 and 2% Ar, forget about the argon. However, CO is a completely different story...

 

[miketsp]

I would not dive on a boat that had 95% oxygen as their emergency surface DCS treatment gas, nor would I buy gas from a source with 2% argon. There are other methods that do not have these drawbacks.

The OP's context is a liveaboard system. This presupposes that there are not many shops around to buy gas from.
At the surface 5% Ar in 95% O2 shouldn't present any issue as per the article I quoted.

 

[ianr33]

Although considered one of the 5 inert gases it can produce some compounds but nothing that should be significant.

Argon compounds are laboratory curiosities. Not a problem in a scuba tank!

<<By shining ultraviolet light onto frozen argon containing a small amount of hydrogen fluoride, argon fluorohydride (HArF) was formed. It is stable up to 40 kelvin (&#8722;233 °C). The ArCF2+2 metastable dication was also observed.>>

From Argon - Wikipedia, the free encyclopedia

 

[Lobzilla]

Thanks to everyone for their input.

Since the original posting, I found out that the US Navy generates Oxygen the same way on the largest aircraft carriers. The only difference is that they also bottle the Nitrogen for inflation of landing gear struts and other purposes. The concentrated Oxygen, with corresponding amounts of Argon, is compressed via oil-less Rix compressors and used directly as Aviator Oxygen. What I could not find out is whether the same stuff is used to create gas mixes for diving. Maybe someone currently serving could inquire.

I agree that potential CO contamination is a serious issue and have taken appropriate precautions through location of the air intake and by using an in-line CO monitor.

BTW: I am working on the completion of the first prototype and will post results
here as they become available.

 

[Mr.X]

Looking forward to the results of your prototype.

On a totally experimental and goofy nature (in the early days of mixed gas tech diving) we tried argon just for the heck of it. We had some extra in a bottle for drysuit gas and tried a swig of it along with some surface air. WOW. Weird stuff and not in a nice way too. The only way to describe it was off-color and repulsive. You wanted to breathe straight air immediately.

 

[Garth]

You could do research like the navy: find young healthy men and subject them to your test gas and see what happens. Increase percentage and repeat. First person to be injured or worse is the limit to allowable percentage of diveable argon...
Am I correct?