This paper advances the thesis that a complete assessment of the chemical process safely must be founded on specific chemical hazards data. Usually these data can only be obtained from appropriately designed experiments using the correct testing techniques. The basis of safety and the window of safe operations arise from. the relevant process safety data. BakerRisk's experience with the chemical processing industry (CPI) has shown that the PSM elements Safety Information, Process Hazards Analysis, and Operating Procedures are, often documented without adequate hazards test data for the covered process. The information is often qualitative; it may be taken from inappropriate laboratory data and may not address the specific process deviation or worst-case situation(s). This lack of hazards test data represents an information void that tabletop or literature process hazard analyses alone cannot fill. Five observations and recommendations are offered: .Chemical process safely supported by hazards testing is the right thing to do, whether the process is covered or not and whether the process is at the manufacturing stage or not; . Hazards testing to identify and evaluate potential upset conditions should be an integral part of a company's process safety program. It is a major information source for process hazard analyses; . The information obtained is specific to the thermodynamics and kinetics of the process chemistry; . The information enables clear identification of operational, thermal, and reactivity hazards of processes involving highly bazardous chemicals; . The scope of the chemical hazards testing should be matched with the quantities of chemicals involved and the development stage of the product. (C) 2004 American Institute of Chemical Engineers Process.