Thermal comfort characteristics and heating demand of people with different activity status during extremely cold exposure

Extremely cold weather frequently occurs worldwide, increasing the risk of exposure to extremely cold environments, particularly for outdoor workers. Cold stress can significantly reduce work performance and impair workers' health and safety. However, few studies have focused on the thermal comfort characteristics and heating demands of people involved in different activities during extremely cold exposure. Herein, 18 male subjects were recruited to perform different activities in a cryogenic chamber with an ambient temperature of 14.0.C. They underwent 15 min of standing adaptation, 40 min of heating and 15 min of standing recovery. During the heating phase, they experienced four activity status with adjustable heated garments switched on: standing, continuous 4 km/h and 6 km/h walking, and intermittent 4 km/h walking. Variations in subjective perception, physiological responses and heating parameters over time were recorded throughout the experiments. The thermal sensation zone corresponding to thermal comfort shifted and expanded towards the warm side, which may be attributed to local cold exposure. Subjective feedback and self-adjustment were combined to quantify heating demands. Thermal comfort and energy savings were simultaneously considered when determining the heating demand. The comfortable temperature inside the clothes for standing was 23.5-32.9.C, and active heating was not required for walking at 6 km/h. The actual heating demand decreased with increasing activity intensity and was much lower than the commercially heated garments provided. Heating strategies for different activity status were recommended to guide the design of personal comfort systems.