Recommended procedures were set forth for safe entry and working in confined spaces. The criteria document was designed not only to make the work safe but to make the worker aware of the hazards and instill in him the necessary work practices to overcome and deal with these hazards. Relevant terms were defined including not only such terms as atmosphere, ceiling level, combustible dust, permissible exposure limit, oxygen deficiency, lower flammable limit, and confined space, but different classes of confined spaces. A Check List of Consideration was given which delineated the minimum preparation required for each class of confined space entry. Various types of permits required for confined space entry were discussed. Requirements for medical supervision, training of workers, testing and monitoring the atmosphere in the confined space labeling and posting of confined space areas, safety equipment and clothing required to protect the worker, and good work practices such as purging and ventilating, isolation/lockout/tagging, cleaning, selection of tools, and recordkeeping were listed. Hazards associated with confined spaces were discussed, including various types of atmospheres (flammable, toxic, irritative and asphyxiating, as well as mechanical failures, communication problems, physical difficulties in entry and exit, thermal conditions, noise, and vibration. Industries in which entry to a confined space may be necessary included agriculture, fishing, hunting, trapping, oil, gas, construction, food processing, textiles, lumber, woodworking, furniture, paper manufacturing, chemical, petroleum, rubber manufacturing, leather, stone processing, metalworking, electrical, transportation, shipbuilding, communications, auto dealers and gas stations, restaurants, and real estate.