Compressors represent a multimillion dollar investment for many plants‎,‎ and profitability can be neither reached nor sustained by organizations that neglect this critically important asset‎.‎ This is clearly brought out in more detailed compressor texts‎;‎ these are available and listed in the references‎.‎ However‎,‎ whereas these more detailed texts have often been recommended for and by machinery reliability professionals‎,‎ a condensed overview of compressor design‎,‎ operation‎,‎ and maintenance is desired by other job functions and will thus be given in this book‎.‎ This material will assist the very wide spectrum of readers whose process involvement brings them into contact with large process compressors‎.‎ As an example and to run a smooth organization‎,‎ terminology must be unified and misconceptions dispelled wherever they creep into our thinking‎.‎