The fuel:air ratio for getting high is way richer than the fuel:air ratio for combustion. Also if you're getting high off it you're probably not going to want to waste it. I'm assuming butane was the propellant for the air freshener since IIRC that's a common propellant for things that are supposed to smell nice.

https://www.mathesongas.com/pdfs/products/Lower-(LEL)-&-Uppe...