Culture of Safety
Parasite reactions which had never been observed before occurred within the storage tank of an intermediate product, producing heat. Even if the molar heat of reaction was small, the quantity of material in the tank was considerable; the thermal insulation good, and over a long time (weeks), the temperature increased to dangerous levels. There apparently were other minor equipment problems, and the whole chain of events resulted in an explosion and subsequent fire. Anyway, only three workers were mildly intoxicated by the fumes.
How did all this became clear? Because the company conducted an internal in-depth investigation on the incident: believe it or not, but corporations don't really like it when their plants blow up. Anyway, the lessons learned are being applied, and new processes are carefully examined beforehand against the possibility of these parasite reactions.
All this is possible because this corporation does care about safety in the first place, and has policies and procedures in place (like other companies do, of course).
The most infamous incident of the chemical industry, instead, occurred at Bhopal with catastrophic consequences (thousands deaths, among them) and it was caused by a long string of events - some imputable to the management, but some more insidious and related to the local culture. Corporations do provide (or at least are supposed to) proper training to the workers, but I'm not sure it can override a worldview formed in years by family, peers, schools, churches/mosques and all that. According to some sources, the prevalent local culture at Bhopal (a mainly Muslim area) was very fatalistic: if Allah wills, the plant will work no matter what, but if He doesn't want, the plant will fail despite any human effort.
I've seen personally, and heard many stories of people who learnt to do a job the old way, and are not going to change even if there are new and better ways of doing the job. I think that the proper safety culture can only be instilled in a workforce that is already receptive to it; otherwise safety will always remain a secondary concern. workers will behave until they are closely supervised, but revert to the old habits as soon as they can. And yes, I have firsthand experience of that too - fortunately, not in safety-critical situations.