Physiological and psychological responses while wearing firefighters’ protective clothing under various ambient conditions

Firefighters are required to carry out their responsibilities under a wide range of environmental conditions. For this reason, the physiological and psychological responses of firefighters while wearing their protective clothing should be analyzed to minimize their thermal or cold stress. Four environmental conditions were selected: hot and humid (HH, 34℃, 75% relative humidity (RH)), hot and dry (HD, 34℃, 30% RH), warm and dry (WD, 27℃, 30% RH), and slightly cold (SC, –3℃). Six professional firefighters served as subjects. The exercise was performed on a treadmill at the maximum speed of 8 km/h. The microclimate temperature and RH, skin temperature, heart rate, oxygen uptake, sweat loss, sweat evaporation, moisture accumulation within the outer shell, moisture barrier and thermal liner, and subjective sensations were measured. The microclimate wet-bulb globe temperatures (micro-WBGTs) were calculated. High microclimate measures, skin temperature, and heart rate, as well as low scored subjective sensations, were observed under the HH condition. A 45% difference in RH between HH and HD resulted in clearer differential responses compared with the 7℃ difference in air temperature between HD and WD. Under the SC condition, subjects had a cool to cold feeling. A quite different distribution of moisture accumulation in clothing layers was observed under the SC condition compared with other conditions. This moisture accumulation affected the comfort sensation. A linear relationship was found between the comfort sensation and the micro-WBGT. The micro-WBGT was a good indicator of the physiological status of the wearers. The microclimate, moisture accumulation and its distribution within firefighters’ protective clothing should be extensively studied in the future.