Introduction The hardship at work in the steel industry is linked to the important thermal constraints related to production processes. This study aims to identify the heat strain at work in the steel industry in Tunisia through the assessed metabolism by cardiovascular heart rate recording and to evaluate the thermal stress based on the various of measurable parameters.

Methods A cross-sectional exhaustive study was conducted among the 80 workers in a steel company. The recommendation of the ‘analysis’ level of the international standard ISO 8996 ‘ Ergonomics of the thermal environment -- Determination of metabolic rate was adopted for the evaluation of the thermal strain. The international standard ISO 7933 ‘ Ergonomics of the thermal environment -- Analytical determination and interpretation of heat stress using calculation of the predicted heat strain’ was adopted for the assessment of the thermal stress.

Thus, metabolism was evaluated based on the recording of heart rate during work withen steel workers. Moreover, physical parameters of thermal stress (air temperature, relative humidity, air velocity, globe temperature, clothing isolation, working metabolism) were assessed.

Results The equivalent metabolism was equal to 292.7 W±59.8 W. Thus, workload was ‘acceptable’ for the majority of workers (84.8%). Concerning the thermal stress level, 68.18% of the subjects were at risk of a long-term constraint (discomfort and risk of dehydration after several hours of exposure) and 30,3% of them faced a short term constraint (risk for Health after 30 to 120 min of exposure).

Discussion The present study objectively quantified the physical workload in the steel sector. For most workers, the workload was light to moderate. The long-term and short-term thermal stress objectified in this study was the source of a workstation layout and a prevention strategy.