Abstract:

Objective The entire firefighters' protective ensemble includes the turnout gear and base clothing worn. The base clothing is always worn contacting the firefighters' skin and would influence the temperature and relative humidity within the clothing microenvironment as well as the heat and moisture transfer through the garment. This study aimed to investigate the influence of the base clothing on firefighters' physiological and perceptual responses. The outcomes of this study were expected to reveal strategies for combining the optimum clothing style and fabric type of base clothing to improve firefighters' thermal responses and efficiency.
Method A survey was conducted and 203 firefighters' data were collected about the fabric types and configuration styles of the clothing that they wore under their turnout gear. Four base clothing combinations were obtained. Physiological experiments were conducted to detect eight subjects' skin temperature (T_sk), heart rate (HR), galvanic skin response (GSR), overall discomfort sensation, heat sensation, wetness sensation, and adhesion sensation when wearing four types of test samples. Repeated measure analysis of variance was used for the main effects (P<0.05). A four-scale analytic hierarchy process (AHP) model was adopted to determine the comprehensive score of the four base clothing combinations.
Results In the stage of the exercise, S1 presented the lowest T_sk (36.78±0.57) ℃ and was significantly 0.5 ℃ lower than S3 (P=0.00). It was interesting to observe that S2 presented the lowest growth rate of T_sk at the end 10 min of exercise and was 1.8% lower than S3. During the recovery, subjects had the lowest T_sk when wearing S2, which was 0.30 ℃ lower than S3 (P=0.01). The variation of HR was consistent with the result of the T_sk (Fig.6). In comparisons among four test samples, a lower HR in S2 was detected throughout the test. Especially, HR in S2 was 4.31 bpm lower than in S3 (P=0.02) in the exercise. During the recovery stage, HR in S2 continued to be lowest, even where no significant differences were noted (P>0.05). The minimum GSR was reported for S1 among four test samples (Fig.7), which were 1.75 μS lower than S3 (P=0.04). During the last 5 min of exercise, the growth rate was the smallest when wearing S2, which was consistent with the T_sk. The wetness rating in S2 was significantly lower than that of the S3 by 20.37% (P=0.01) during the exercise (Tab.2), which was consistent with the lower GSR in S2. It was also found that the sensation was different in varied body parts. The torso and thighs had the strongest feeling of heat and moisture, and the forearms, knees, and calves have the strongest contact discomfort, such as adhesion and roughness. The AHP model showed the cotton/polyester short-sleeved combined with camouflage trousers had the highest overall score (Tab.3), which facilitates the evaporation of sweat from fully clothed individuals working in high-intensity, thereby reducing the risk of firefighters' thermal strain.
Conclusion Base clothing had impacts on firefighters' physiological or perceptual responses during the exercise and recovery periods. Fabric properties of base clothing, especially sweat evaporation, were observed to have a primary contribution to subjects' thermal responses, no matter what the clothing style was. A cotton/polyester fabric with long pants would be a favorable solution for firefighters to alleviate thermal strain which did not compromise the protection. The optimization of firefighters' base clothing should consider the design of functional zones, such as splicing moisture-permeable and breathable fabrics on the chest and back and splicing flexible fabrics on the calves.

Key words: firefighter, turnout gear, base clothing, physiological response, perceptual response