It seems that since they phased out chloroflourocarbons, fuel gasses like propane and butane have become the propellants of choice: http://www.ehow.com/about_6468524_pu...products_.html

But it's odd that you don't hear of more accidents like this one; 3D printers are hardly the only source of sparks. I wonder if there wasn't also a gas leak in that magic shop. In the meantime, make sure your printer's turned off when you spray, and be careful about what You-tube videos you try to replicate at home.