ABSTRACT

There are many methods and thermal indices which can be used in the assessment of hot environments but none is directly applicable to work in compressed air environments. The International Standards Organisation (ISO) has recently published standards for the assessment of hot, moderate and cold environments, and ISO 7933:1989 provides an analytical approach to assessment of hot environments. The sweat rate required to maintain a worker in thermal equilibrium is calculated from values of air temperature, humidity, mean radiant temperature and air velocity in the environment and estimates of clothing insulation and metabolic heat production of the worker. This (SW req) value is compared with sweat rates which can be achieved by workers to provide a basis for determining working practices in the environment. In compressed air environments, equations for calculating the heat exchange between a worker and the environment and also the physiological capabilities of the workers will differ from those presented in ISO 7933.

ISO 7933 has been proposed as a European standard which would then become adopted in the United Kingdom. This paper considers the appropriateness of ISO 7933 for the assessment of hot conditions in compressed air work.