Electrically heated sleeping bags could improve the human feet thermal comfort in cold outdoor environments

In this study, two novel electrically heated sleeping bags were developed by inserting heating pads into two traditional sleeping bags at the foot region. The physiological and psychological responses of six human subjects (3 males and 3 females) while wearing the non-heated sleeping bags (i.e., when heating power was turned off) and the electrically heated sleeping bags (i.e., when heating power was turned on) were examined. It was found that the electrically heated sleeping bags could dramatically improve and maintain the microenvironment condition at the feet area within the thermal neutral range (i.e., 24-34 °C). Besides, the heated sleeping bags significantly improved the subjective perceptions at the feet. In contrast, the toe temperature of the subjects in the non-heated sleeping bags dropped linearly to 15°C and cold discomfort and pain sensations were reported at the end of the 3-hour cold exposures. It was thus concluded that the new electrically heated sleeping bags could effectively improve the human thermal comfort at the feet.