Presentation of criteria and recommendations for a standard for work in hot environment. The criteria are developed to assure that the standard would provide protection against heat induced disease, be attainable with existing technology and amenable to valid, reproducible techniques available to industry and official agencies. The criteria are based upon extensive review of the known biologic effects of heat exposure, environmental and control data. The work practices standard is designed to prevent primary heat disorders, heat induced unsafe actions, and harmful effects which may arise from the interactions between heat and toxic chemical and physical agents. The environmental measurements are not intended as an upper limit for occupational exposure, but only a level at which work practices must be implemented.