Impact of wearing indoor masks on occupant's thermal comfort under different room temperature conditions in winter

In the period of coronavirus pandemic (COVID-19), wearing a mask was a mandatory measure to prevent the spread of the virus. After the pandemic, a large percentage of people answered that they would wear a mask to protect themselves and others. However, the mask would directly affect not only the thermal sensitivity of the face but also occupant's thermal sensation. In this context, this study aimed at clarifying the effect of mask on occupant's thermal comfort. The predicted mean vote (PMV), predicted percentage of dissatisfied (PPD) and thermal sensation vote (TSV) were evaluated in a chamber where the set temperature was maintained at 20 degrees C, 22 degrees C and 24 degrees C with and without a mask. When wearing a mask, the TSV mostly exceeded the comfort range and showed a more sensitive variation than the PMV. In addition, the mask dead-space temperature showed a significant difference when the room temperature was increased from 22 degrees C to 24 degrees C. The room temperature that affects the individual thermal comfort with masks was 24 degrees C or higher. Room and mask dead-space temperatures showed a 55% correlation with TSV. This study would provide basic data for determining the optimal room temperature for occupants with masks by identifying the room temperature that could significantly affect thermal comfort of occupants with masks.