I remember this dude putting a bunch of materials to the test with a direct blowtorch flame. https://www.youtube.com/watch?v=8NC79e0oztM. I was hoping he had a demo of denim; it's mentioned in the video description, but skimming the video I couldn't locate it in a reasonable time. You can look at his demo on treated cellulose around 1:48
bummer ><, I was hoping it would perform a lot better. The brief coverage of the poor performers explains why I couldn't skim it and land on it. Only the strong contenders had long enough coverage to skim with a mouse hover over the timeline and spot them in the thumbnail. Sounds like it was trading on low allergic response vs flammability according to his commentary.