Based on the twitter cloud and the very fragmented and contradictory information so far, it is not possible to know why a West, Tex., fertilizer plant exploded last night with casualties and property destruction. This is not the first time a fertilizer plant has self-destructed, of course.
I am struck by one thing. According to most reports, the explosion itself occurred about two hours AFTER the West Volunteer Fire Department responded to a fire at the plant. Since it appears there were heavy casualties among the first responders we don't know yet what happened.
I can only guess. There were tanks containing 54000 pounds of anhydrous ammonia on the plant site, according to a report filed with the State of Texas by the company. The anhydrous ammonia is in liquid form under pressure under normal conditions. If the Volunteer Fire Department was not trained in how to respond to an ammonia fire, it is possible they could have been the proximate cause of the explosion by combining water with anhydrous ammonia leaking from a ruptured tank.
Why do I think they might not have been trained properly? It isn't because they were volunteers. I have worked with volunteer fire departments who were every bit the equals of full time professionals in training and operational safety. No, the reason is that the hazard plan the West Fertilizer Co. filed with the State and the EPA claimed that there was no danger of explosion, and that at the worst case, there would be a short (10 minute or so) duration ammonia gas leak, which would dissipate on its own.
In short, the company seems to have minimized the potential for disaster. This must have been reflected in their safety planning, right? After all, you don't plan for explosions if you've told the regulatory bodies that there won't be any. It doesn't look good, and might call your HAZOP into question.
This may be another in the great chain of accidents caused by adherence to legal conformity and compliance to the letter of the regulations, while ignoring the need for actual, enhanced safety in operations.
Follow the twitter feed #pauto where I will be posting more information as I get it.
And above all, my deepest sympathies and prayers go out to the victims of this tragedy.