In one of these threads I saw a spreadsheet of the derailed cars, and there are a bunch with dry bulk materials. These were the source of the fire that was/is b

In one of these threads I saw a spreadsheet of the derailed cars, and there are a bunch with dry bulk materials. These were the source of the fire that was/is burning [0], and included a few listed as containing "POLYVINYL". I couldn't really figure out what that was, whether it was PVC pellets or a different polymer or what. There was an article posted last night [1] (now flagged) talking about dioxins. It showed a picture of 2,3,7,8-TCDD [2], with two benzene rings, and talking about its longevity due to those. I've only got a rudimentary knowledge of ochem, but my first thought was wondering where those benzene rings would come from in the burning of vinyl chloride. My conclusion was that the article was conflating different types of dioxins as a single thing - if dioxins are being created by the burning of the vinyl chloride, it's likely the simpler 1,4-Dioxin [3] which according to Wikipedia "is very unstable" so probably will not last long. This is all guessing on my part, but it still feels more in depth than most of the reporting/discussion has been trying to independently analyze. [0] Which necessitated doing something about the adjacent tanks full of vinyl chloride, which are seemingly under some pressure (PRV @ 225psi) but mostly rely on keeping a lower temperature over the course of their journey (at least that's what I gathered from reading the spec sheet of a DOT-105 tank car meant for transporting vinyl chloride) [1] https://news.ycombinator.com/item?id=34800306 https://news.ycombinator.com/item?id=34800306 [2] https://en.wikipedia.org/wiki/2,3,7,8-Tetrachlorodibenzodioxin https://en.wikipedia.org/wiki/2,3,7,8-Tetrachlorodibenzodiox... [3] https://en.wikipedia.org/wiki/1,4-Dioxin https://en.wikipedia.org/wiki/1,4-Dioxin