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One of the most useful tools for evaluating the reliability and safety aspects of a life support system is the Failure Modes and Effects Analysis (FMEA). Using this technique an analyst develops an orderly assessment of the cause, effect, and possible prevention of potential equipment failures. The analysis produces a unified document listing potential failures and causes which are studied at the system level. When used early in the design stages, recommendations for corrective actions can be economically incorporated. This work describes how Westinghouse Ocean Research and Engineering center engineers use the following procedure to analyze failure modes and their effects on a system during the early design stages. The analysis begins with the preparation of a block diagram showing the interrelation of all components in each sub-system and the input and output of the subsystem. A subsystem breakdown for a typical SCUBA shows three diagrams: (1) gas system, (2) electrical system, (3) water system. Each component becomes a subject for analysis. Next, worksheets are prepared for each listed component. The worksheets form the analysis documentation and contain the following information: mode, effect, cause, and prevention. After evaluation of the complete system, the finalized document is presented to management as a tangible acknowledgement of their requirements to produce safe, reliable equipment. The Failure Modes and Effects Analysis thus evolves into a management tool. A tool that serves to provide the impetus for insuring that all conceivable failures are considered and resolved as well as a tool for insuring the embodiment of failure prevention methods into system documentation.