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Yes, O2 is O2 (almost!). The highest quality O2 that is available is Medical Grade, but the average person cannot get it. The next grade of O2 is Avation Grade. I do not know for sure exactly, but is most likely extremely similar in quality to medical except is not certified medical grade (this is what I use to mix my gas). The poorest quality is welding grade, which is not monitored at all for quality, and is not required to be filtered to remove particulate matter. From a welding perspective the percentage of O2 in the tank is really not that critical. There are also different grades of helium. The lowest grade is that which is used for filling helium balloons, and should be avoided for diving purposes, welding grade which is the next step up is similar to welding grade O2 in quality. Military or medical grade helium is the one to use because the gas is filtered and cylinders are controlled for quality of gas. The explosion/fire risk is essentially the same for each grade of O2. You are probably correct, most welders do not wash their hands, but the risk of fire/explosion from changing an O2 reg with dirty hands is probably nill. O2 is explosive when exposed to hydrocarbons at high pressure, any O2 leaking from the reg or bottle valve is immediately reduced to 1atm and diluted in the ambient atmosphere. An interresting anecdote: I am an engineer for a company that designs custom test machinery to inspect for leaks in vessiles (gas tanks, evaporator cores, a/c compressors, etc...), we use a technology called Helium Mass Spectrometry, where we fill the test object with helium tracer gas and "look" for heluim outside the test object. A while back, I was starting up a machine I designed, and I connected a Nitrogen tank to the test object to confirm the machine cycle before introducing the helium which sometimes causes another set of problems. This time I kept getting what appeared to be minor heluim leaks from the test opject. After several hours, I determined that the nitrogen tank contained helium gas even though the bottle was the correct paint color to indicate nitrogen. The most important thing to be aware of when buying your own gas for mixing is to know what you are getting, and welding grade gasses are not controlled to the same degree that the avation grades are. Russ Nolet ----- Original Message ----- From: p k <abyss30@ho*.co*> To: <techdiver@aquanaut.com> Sent: Saturday, November 27, 1999 8:05 PM Subject: Isn't oxygen, oxygen? > This question has plagued me for a while. > What is the difference between breathing oxygen and welding oxygen? > > First,I was told that welding O2 had more hydrocarbons contained in > it, BUT isn't the explosion/fire risk the same? How many auto mechanics wash > and dry there hands before changing a regulator on an > oxy-acetylene torch? The second thing I was told is "there is possibly a > higher moisture content", to me that doesn't hold up either because oxygen > (commercial grade) will always come in a steel cylinder, if there is any > moisture in there it will rust and pretty quickly I might add. So what's the > deal? Anybody? > > ______________________________________________________ > Get Your Private, Free Email at http://www.hotmail.com > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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