AbstractMany process hazard analyses (PHAs) provide insufficient detail to be able to perform layers of protection analysis (LOPA) studies properly using their results. LOPA teams experience difficulties, when PHA studies are performed without regard to the information needed for LOPA. The LOPA team must develop any needed information missing from the PHA. Not only does this require additional time and effort but it also detracts from performing LOPA. Furthermore, the LOPA results may be inaccurate, as the LOPA team may not develop hazard scenarios correctly. This article provides guidelines for PHA worksheet entries that help avoid these problems to ensure efficient and effective LOPA studies. © 2012 American Institute of Chemical Engineers Process Saf Prog, 2012