Thermal sensation of the body as influenced by the thermal microclimate in a face mask

Subjective and physiological responses were obtained from six subjects wearing a face mask while exercising (220 W m −2 ) for 15 min on a bicycle ergometer. Different combinations of ambient air temperatures (7, 16 and 25°C) and mask air temperatures (22,27 and 33°C) were studied with two different air humidities inside the mask (61 and 86% relative humidity (RH)). Control experiments were performed without the mask at the same ambient temperatures. Skin temperatures, heart rates and skin wettedness were monitored during exercise. The subjects' thermal sensations, sensations of sweating and skin wettedness and their thermal preferences were assessed at the end of the exercise period. Whole body thermal sensation was primarily determined by the ambient air temperature, but was also significantly influenced by the mask air temperature. This could only partly be explained by the change in respiratory heat loss. Other possible avenues of influence are discussed.