It is not fair to assume that the Lima Emergency Management team was wasting their time monitoring the atmosphere for lethal gases.
Cyanide gas in particular can be liberated from the burning of certain hydrocarbons. If you have propylene and nitrogen in combination under superheated conditions the gas can be formed. There is plenty of propylene in crude and the atmosphere is 78 percent nitrogen so the components are there.
The article made it sound like the refinery and responders were knowingly negligent.
It is true that the residue from the soot and ash will contain hydrocarbons. Crude oil in itself contains numerous carcinogenic compounds.
When you have an emergency there is only limited analysis that can be performed. Technicians are sent out to monitor the community for a number of hazardous gases. They are pulling air over a conditioned tube that will depict parts per million of a specific component. It’s good to know there was no cyanide liberated.
Later when the emergency is controlled they will analyze for the actual long-term hazardous potential.