Face Temperature as an Indicator of Thermal Stress in Outdoor Work Environments

The frequency and duration of heatwaves are steadily increasing as climate change becomes more serious. These changes particularly endanger the health of those who must work outdoors in hot environments. This study introduces a novel approach to monitor the heat-health of airport outdoor workers using infrared thermography. The faces of airport workers who were refueling airplanes in extreme heat conditions were monitored using a thermal infrared thermometer during their work cycle throughout the day. Changes in temperature on their exposed faces (e.g., the ear, cheek, chin) were monitored throughout the day over a two-month period. In every test, the subject's face temperature increased, then suddenly dropped for a short time, and then continued increasing. Subjects were also asked to assess their thermal perception of the work each time they were tested throughout the study. They reported that they felt discomfort in terms of thermal comfort when the facial skin temperature went down temporarily before the temperature rose. These results show that the physical measurement criteria when outdoor workers' thermal health is in jeopardy can be based on the results of facial skin temperature measurements.