An abbreviation for hazard and operability, it is a systematic and structured hazard evaluation technique used to identify the potential failures of equipment or plant systems that may otherwise become hazards and present potential operating problems. The aim is to eliminate or minimize the probability of an incident from occurring and the severity of consequence arising from that incident. It uses a multidisciplinary team-based approach to consider what can go wrong, the causes, consequences, frequency of occurrence, measures for prevention, and justification of the associated costs of prevention. The study uses guidewords for the possible deviations from an intended design or operation of a process. These include none, more of, less of, part of, more than, and other, and in each case is applied to the effect of flow, temperature, and pressure. It also includes the effects of impurities, changes in phase and composition, extra phases being present, and activities that can happen, as well as normal operation such as maintenance, purging, access, start-up, shutdown, alternative operation mode, and failure of plant services. The HAZOP team works systematically on a particular point in the process and considers a particular parameter such as flow, pressure, temperature, level, heat, and deviation. The causes and consequences are recorded along with any required action to improve the safety or operability of the process. On completion, the next guideword at the same node is considered until all the nodes with their parameters and deviations have been considered. Finally, the costs of recommended changes to the design or plant are reviewed and justified.