Toss them ALL in the firepit ato nce and take apic
That was my first thought, sort of, except I was going to tape the valve open, light them, and see where the point of actual failure (poof!) was. Cool to watch, from a distance.
But having identified a potential point of failure in gear I rely on, I'm going to see if I can light the butane "tinder" with a spark (stainless knife + rock). Shouldn't need a very hot spark.