Hazard analysis is a crucial task in plant design. It is expensive in terms of money and time, and involves many specialists in different disciplines who are required to analyse aspects dispersed throughout the plant documentation. Product Lifecycle Management systems allow all the project data to be handled in a complete, integrated and consistent manner; they permit tools to be developed for capturing and reusing the design information necessary to evaluate specific plant aspects concerning potential hazards, thus providing automatic verification of some safety criteria. In this paper we present a knowledge-based tool aimed at supporting the expert in performing HAZOP studies in a plant project managed by a CAD/PLM system. The tool is based on an extended plant model that includes all the data and relationships representing the knowledge on which the supported hazard identification method is based. (C) 2006 Elsevier Ltd. All rights reserved.