Answer: Propane
Why: When anything other than propane, If you huff and puff in an enclosed basement while working, you start seeing some weird stuff. A genius at work forgot to open the windows... His eyes are as red as the devil's dick.
The reasons for huffing glue, paint, and gasoline, are far different than the reasons propane in an enclosed area. The dragons right though, propanes made from crude oil refining as well as natural gas refining.