On February 3, a Norfolk Southern train carrying hazardous materials derailed near the town of East Palestine, Ohio. Fifty cars derailed, ten of which carried hazardous chemicals. Federal investigators say a mechanical issue with a rail car axle caused the derailment.

A fire broke out in the rail cars, residents were evacuated, and the material in some of the cars was drained and set on fire. Draining the material prevented a BLEVE, a boiling liquid expanding vapor explosion, which is what happens when tanks of liquid are heated in a fire. A breach in a hot tank like this releases both chemical energy when the liquid explodes and the heat energy as the liquid flashes instantly into a gas. These explosions are extremely powerful.

But then they had to do something with the liquid, so they burned it, producing a thick black cloud of smoke.

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