In this paper the results of a multi-year analysis of the pressure relief devices located in several plants in major chemical sites are summarized. The analysis consisted of a systematic evaluation of existing safety valves and rupture discs including the identification of the service conditions and design cases as well as the sizing calculations of the individual device and associated piping. Furthermore, from the total amount and the hazardous potential of the effluents the necessity of retention systems is evaluated to ensure a safe disposal. Because the knowledge in the field of emergency pressure relief changed very rapidly in recent years, the design of some safety devices was not according to the state of the art. An essential part of the verification program was the recommendation of measures to find the most economical yet technically correct way to correct these deficiencies. Rather than by carrying out wholesale replacement of an incorrectly sized safety device or vent line, often a reduction of the mass flow rate to be discharged, for example, by an orifice in a supply line, is sufficient. Results of the analysis were recorded on a novel database to capture the sizing information and maintain correct pressure relief device sizing into the future. The systematic databased approach has been used for the evaluation of about 4000 safety devices so far. The procedure has been proven to enable an experienced design engineer to carry out the analysis of a great number of pressure relief devices in a time-saving, reliable and reviewable way. (C) 2002 Elsevier Science Ltd. All rights reserved.