Occupational Diseases, A Guide to Their Recognition, Revised Edition. Key MM, Henschel AF, Butler J, Ligs RN, Tabershaw IR, eds., Cincinnati, OH: National Institute for Occupational Safety and Health, 1977 Jun; :497-508
Physical hazards relating to atmospheric variations which employees may encounter on the job are discussed, including heat, cold, hyperbaric environments, and hypobaric environments. The interchange of heat between man and the environment is guided by four factors: air temperature, air velocity, moisture content, and radiant temperature. When heat loss in an employee does not keep pace with heat gain, the core temperature begins to rise causing certain physiologic mechanisms to take over, including dilation of certain blood vessels and a concomitant increase in circulating blood volume and cardiac output. Generally, industrial heat exposures are classified as either hot/dry or warm/moist. Prolonged heat exposure causes irritability, lassitude, decreased morale, increased anxiety, inability to concentrate, heat rash, heat cramps, heat exhaustion, and heat stroke. Permissible heat exposure threshold limit values are tabulated. Physiological mechanisms also become active in cold environments to maintain thermal homeostasis and include peripheral vasoconstriction. Harmful effects of cold exposure include frostbite, trench foot or immersion foot, general hypothermia and vascular abnormalities. Exposure to hyperbaric environments may result in primary or secondary pressure phenomena, or decompression, while hypobaric environments may cause dysbarism, impaired judgement, malaise, headache, nausea, vomiting, and pulmonary edema.