27 April 2019
Scariest photo I've seen all year
That white cloud on the ground is anhydrous ammonia flowing across an Illinois suburban neighborhood after an early morning accident involving a tractor transporting a tank to a farm field.
I used to give lectures on the hazards of toxic gases, and while the war gases like phosgene and mustard gas are fascinating, the more relevant risk for civilians is exposure to ammonia and chlorine. Anhydrous ammonia accidents usually occur in rural locations while using equipment like this:
The gas is also potentially flammable, which is why hazmat officials advised residents near the spill to turn off heating equipment while sheltering in place.
Top photo via and some discussion here. Lower image cropped for size from the original.