Before I begin, nothing I am going to say in this article is required by OSHA or EPA; however, keep in mind that OSHA and EPA process safety requirements are the BOTTOM OF THE BARREL when it comes to true process safety. So with that said, let’s discuss PHA scenario likelihoods. Regardless of methodology used, at some point during a PHA someone will through out the notion “that will never happen!” For some strange reason I find the sceanrios that the facility believes would never happen, one that has a high probability of occuring. Here’s an example and some data to consider.