Posted By IanD Hi Barrie This subject can get very complicated. The assessment is fairly simple to do; it is all the information you have to get to enable you to carry out the assessment that is the problem. You have to know the dispersion effects of toxics, the thermal loading of a fire, energy levels from a BLEVE etc Information regarding the construction of the building, the No of persons inside, the time occupied, the chemicals store and used within areas adjacent to this building, the effects of an incident involving theses chemicals on that building and its occupants, roof loading etc. I will e-mail you a sample assessment, and remember the assessment is assessing if the persons in the building or at more risk from an incident by being in the building