The chlorine doesn't turn into CO2. HCL reacts with everything and turns into salt and water. But it reacts so rapidly and so readily that it was basically all

The chlorine doesn't turn into CO2. HCL reacts with everything and turns into salt and water. But it reacts so rapidly and so readily that it was basically all used up well before the evac order was lifted (possibly, the area will see a little acid rain, but not as bad as in the era of un-scrubbed fossil fuel plants everywhere. And acid rain doesn't mean "you go outside and melt;" it's hard on paint, plastics, open water, and plants because it effs with the pH, but at the concentrations from a few train cars spread over hundreds of square miles, life will handle it. Better than leaving the vinyl chloride concentrated in one place to do damage and then denature into HCL on its own). Most of the visible chunk of the cloud is soot (solid carbon chains). The EPA has recommended cleaning up the soot where it lands. ... And they are currently doing ongoing air quality testing, yes. The tests continue to show acceptable levels of impurities IIUC.