Board Thread:Questions and Answers/@comment-26932251-20160101213041/@comment-26932251-20160102010530

EternalLocket wrote: I don't think it's ever said that it used compressed air. I think that's from the days before much was said about 3DMG.

So far, every translation of the process I've seen has used gas instead of air. I could have sworn they mentioned what type of made up gas they used, but I also read the spinoffs, so I may be mixing up things. Needless to say, the spinoffs don't apply on something so fairly central in canon.