Human performance under hot thermal condition of work environment

In the summer of 1950, 1963, 1966 and 1973, repeated surveys were carried out on thermal conditions in various industries. Meanwhile technical innovations began to take hold gradually in Japan, causing, in major industries with hot work places, attenuation of heat exposure during work and reduction of the energy expenditure of workers by the replacing of heavy muscular work with machines. Comparison of data of the 1950s, 1960s and 1970s disclosed appreciable improvement of the thermal conditions in major industries which could be attributed to technical progress in recent years. An examination was made of the propriety of the existing legal provision on permissible threshold limit, of 37 degrees C in the coal mine in Japan. Experiments were conducted to investigate changes in some physiological functions and subjective feeling of coal miners during moderate muscular work in a hot and humid experimental gallery. The experimental results seemed to suggest that 34 degrees C of dry bulb air temperature might be a considerably severe condition for coal miners, even in cases of intermittent exposure or continuous exposure with rather frequent work intervals, working under conditions of high humidity and low air velocity at a moderate work rate.