Introduction: Continuous exposure to cold air is considered to be a hazardous agent in the workplace in cold seasons. This study aimed to determine the level of cold stress and relation with physiological responses in auto mechanic employees.

Method: This cross-sectional study was conducted in the winter of 1395 on auto mechanic employees in Hamadan city. Physiological responses during daily activity were measured in accordance with ISO 9886 standard method. Environmental air measures like air temperature and air velocity were measured simultaneously and cold stress indexes were also determined. Data was analyzed using SPSS 21 software.

Result: The result showed that mean wind chill index, equivalent chill temperature and required clothing insulation were 489.97±47.679 kcal/m².h, 13.78± 1.869 ⁰c and 2.04 ± 0.246 clo, respectively. According to the results of cold stress indexes, the studied employees are exposed to cold stress. Pearson correlation test showed that there are significant relationship between cold stress indexes with physiological responses (p<0.05), however, IREQ min showed more correlation than the others.  There is also a significant relationship between body fat percentage and deep temperature (p<0.05, r=0.314).

Conclusion: The result confirmed that IREQ min index has high validity for estimation of cold stress among auto mechanic employees. Moreover, the increase of body fat percentage leads to an increase of cold tolerance power of employees.