This discussion, which started with using butane or propane to top off bottles, got side tracked to compressed nitrogen because butane is too dangerous!!! After reading all this about tank hazards I feel safer with butane and I don't have to chain it to the wall or keep my greasy hands away from it. All I have to do it keep matches away. I have been using candles for a special printing effect but I won't do that any more;-)
I am being a wise a** but it seems to me that butane is still easier, cheaper and maybe just as safe if used appropriately.