The preventive aspects of an occupational health program include the examination of the overall environment created by the work site and production processes. To recognize the hazards of the environment, there must be a familiarity with work operations and an understanding of the effect of various exposures and stresses on health and well-being of the worker. To fill this need, the authors of this manual present a simplified, logical, and organized explanation of the elementary principles of industrial hygiene. The manual is divided into six major parts. The first three discuss the key concepts vital to any effective industrial hygiene program: the recognition of specific environmental factors and stresses, evaluation of hazards, and the application of effective control measures. Part 4 describes the parts of the anatomy most vulnerable to occupational hazards and the methods of monitoring and protecting the lungs, the skins, the eyes, and the ears. An effective