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Wearing protective clothing in high-temperature and high-humidity environments can have adverse physiological effects on the body and become a secondary risk factor that threatens the wearer's safety. Therefore, a solution to this problem should be sought (Zhang et al., 2022). However, studies must systematically analyze the problems of wearing protective clothing or suggest ways to improve wearers' comfort. This study consequently analyzed the efficiency of cooling methods that increase the thermal comfort for healthy level-C (CE Type 3, 4) protective clothing.
The subjects were eight with an average in their 20s provided by the 8th Size Korea Conference (Korean Agency for Technology and Standards, 2021). The following types of experimental clothing were evaluated: Case 1 (protective clothing), Case 2 (protective clothing + coolant), and Case 3 (protective clothing + coolant + fan). The coolant was attached to the neck (3.5 °C) and back (0 °C) and the fan (15.0 °C, 16.6 m/s). Participants had to do a treadmill walking exercise (4 km/h) under the following environmental conditions: 30.0±0.5 °C, 60.0±5.0% RH, and 0.2±0.1 m/s. A 7-point Likert scale was used to evaluate subjective sensations: 'degree of feeling heat,' 'degree of feeling wetness,' 'degree of feeling comfort,' and 'degree of feeling cool.' The temperature and humidity inside the clothing were measured in four areas: bust, shoulder blade, thigh, and calf. Skin temperature was measured on the bust, upper arm, thigh, and calf, and the average skin temperature was calculated using the Ramanathan 4-point method. Thermal images were captured before and after the exercise using a thermal imaging camera. The average surface temperature of the protective clothing was calculated in a rectangular area (30.0 × 50.0 cm) of the same size in the front and back of the upper body.
According to the cooling method, the analysis of the subjective sensations following the exercise revealed that Cases 2 and 3 were significantly (p < .05, p < .01) less hot, less wet, and more comfortable after the exertion. When analyzing the changes in temperature within the protective clothing, it proved to be statistically significant in the shoulder blade after the exercise (Case 1: 35.8±0.7 °C, Case 2: 34.3±1.4 °C, Case 3: 33.7±1.3 °C) (p < .05, p < .01). There was no significant difference in the temperature of the protective clothing in the bust, but Cases 1, 2, and 3 were recorded as 35.6±0.6 °C, 34.6±1.1 °C, and 34.4±1.1 °C, respectively. The analysis of changes in humidity in the protective clothing indicated that the humidity in Cases 2 and 3 was significantly low in the shoulder blade and bust (p < .05, p < .01). The average skin temperature after exercise registered for Cases 1, 2, and 3, were 35.7 °C, 35.2 °C, and 34.7 °C, respectively, reflecting increases of 2.7 °C, 2.4 °C, and 2.3 °C, respectively, from before the exercise. An analysis of the surface temperature of protective clothing according to the cooling method before and after the exercise showed a difference of 5.0°C in Case 1, 4.8°C in Case 2 and Case 3 in the front, 5.3°C in Case 1, 4.9°C in Case 2, and 4.6°C in Case 3 in the back. Overall, suppose the body continuously moves in a high-temperature, high-humidity environment with closed clothing conditions; it reaches the limit of body temperature control, which actively aids the evaporation of sweat generated through coolants and wind with absorbent to relieve thermal stress, and is effective in enhancing comfort.
References
Xu, X., & Gonzalez, J. (2011). Determination of the cooling capacity for body ventilation system. European Journal of Applied Physiology, 111(21), 3155–3160. doi: 10.1007/s00421-011-1941-0
Zhang, Y., Jia, J., & Guo, Z. (2022). Numerical investigation of heat transfer in a garment convective cooling system. Fashion and Textiles, 9, 1-14.
| Keywords | Protective clothing, Thermal comfort, Microclimate, Skin temperature, Thermal image |
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