Prevention of chemical processing disasters largely depends on assessment of thermal stability, mutual compatibility, and decomposition characteristics of materials used in the process. Such studies also facilitate a priori evaluation of vulnerability in operations and can be conveniently organized in the "process development studies" phase of the selected process. However, investigations conducted after the accidents invariably reveal that almost all the major incidents could have been avoided. This suggests an inadequate safety assessment and the vulnerability of a chosen process. Recent literature indicates that, in addition to the areas previously discussed, specific attention should be paid to the behavior of process materials under critical conditions. Quantification of a potential hazard, before an accident, often leads to modifications in design of the equipment and operating conditions, for example, to avoid serious accidents. (c) 2006 American Institute of Chemical Engineers