Stupid question #2

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I asked Number 1 a while back and got exactly what I needed so I thought I'd try again. I read on the Hobart Board about a portable and refillable CO2 bottle that company is offering for use on its small mig units. Several people responded to the post and explained that the setup was essentially the same as the bottle used on paintball guns. The posters went on to explain ways to build one and refill it cheaply. That brings me to my question.I have a small Mapp Gas/Oxygen torch which I use for occasional  brazing. It does a good job on small projects. The problem with the setup is the amount of oxygen it uses and the small tanks it comes in. Very expensive way to braze and you gotta be fast or run out of oxygen.  About seven bucks a pop around here. I can't really justify keeping oxy/acetylene around no more than I use it.Is there any reason a larger tank couldn't be filled with air, propane or freon for example, from an air compressor  to use with a small oxy/mapp setup?  Or is the air we're breathing different than the oxygen at the WS?  The answer may be obvious but...Please be gentle I'm only a solderer. Thanks
Reply:Atmospheric air is made up of 20.9% Oxygen, 78% Nitrogen, and 0.94% Argon, plus some other inert gases.The gas in an Oxygen bottle from your LWS is at least 99.9% Oxygen.
Reply:I just found the answer you gave me in the following link. http://www.hse.gov.uk/pubns/hse8.pdfI had hoped to come up with a less expensive way use the Mapp gas. I guess that's out though.
Reply:Those disposable oxygen cylinders are outrageously priced.If you really really like your torch (and I have to say that those units are pretty awful), you could purchase a REAL oxygen cylinder (but a small one at that), and a regulator, and use it with that torch.  It won't be cheap, but after you go through a few of those disposable cylinders, it will save a fortune.
Reply:Depending on what you braze you might be able to do it with an air acet torch similar to what plumbers and HVAC guys use. I know mine will do silver solder as well as standard solder but never tried to braze with it. I just use my std Oxt acet torch for that if I really need to braze. You can find these relatively cheap on Craigs list. I seen them with the bottle for between $85-$150 depending on the brand. I believe the swirl type torches like Turbotorch get hotter than the std torches like Prestolite, but I have some swirl tips for my Prestolite torch also.