THERMAL STRESS IN A SINGLE STOREY FACTORY

Abstract

Environmental conditions in a single storey factory were investigated as a result of staff complaints in summer when the external temperature rose to 74 deg. F. The Bedford corrected effective temperature scale was used to assess the thermal conditions, from measurements of air temperature, heat radiation, humidity and air movement in ten different parts of the factory. For the greater part of the day, the conditions were found to lie outside the Beford Confort Zone for light work. Measurements of energy expenditure were made in two areas of the factory, i.e. where the worst environmental conditions were found, and where the greatest physical work was involved, to determine whether all the work in the factory was in the light work category of the B.M.A. classification of work. The Wolff IMP respirometer was used to make direct measurements of energy expenditure. In one area, an indirect estimate of energy output was also made by the method of activity sampling, to compare with the direct measurements. The results showed that a significant thermal load is imposed by the environment on those engaged on light work as well as moderate work. Heat radiation from a glass roof and low air movement were the chief sources of the thermal load. Both these factors are commonly found in single storey buildings and they can produce considerable heat stress under summer conditions.