Okay guys, here is my input. I have been running airbrushes and an engraver on CO2 for 15 years now. So I type with confidence. The snow that has been mentioned will never come from an airbrush. I have run mine from 15 psi to 60 psi for usually 3 hours at a time. And this three hours is practically continuous operation. My engraver can ice up the tank and the gauges because of the power needed to engrave aluminum and steel. I solve that problem by focusing a couple of desk lamps on the gauges. I have often been able to write my name in the frost that can form on the tank. It does not affect the tool I am using at all. The only problem with the gauge freezing, is that it can freeze closed. I have also learned the hard way not to lay the tank down while you are going to use it. The flow of the liquid gas froze and busted my hoses. I do not use a water trap or filters on my hoses and I get my gauges from welding stores and the beverage factory.
You just have to understand that a gauge can not always accurately tell the amount left in the tank. You will know best by weighing it. There is a great primer - http://www.cornelius...nual/002811.pdf - (since some replies went off on a gun tangent) - http://www.odcmp.com...S%20drawing.pdf - ( and anyone who likes beer might be able to follow this discussion) - http://www.homebrewt...uestion-334663/
I run 10# and 20# tanks, I have used single action, double action, bottom feed and cup feed airbrushes from paasche, badger and iwata just in case you thought I might not know about your particular setup. I have also engraved 20 - 30 names an hour for up to 5 hours straight on co2.
I better stop now, because I am starting to sound like a know-it-all, but I really am just trying to be helpful.