PDs due to SBS and summary of chi-square test are shown in Tables 8 and 9, respectively. PDs due to the irritations, dry air sensation were in the range of 3–33 and 23–77%, respectively. It was found that PDs due to SBS were insignificantly affected by thermal gradient. PD due to throat irritation was insignificantly affected by room air temperature. On the contrary, PDs due to nose and eyes irritations were significantly affected by room air temperature (p ¼ 0:013 and 0.047, respectivelyrespectively). The results confirm the previous finding that irritations of nose and eyes decreased significantly with increase of room air temperature. PDs due to throat and skin’s dry were insignificantly affected by room air temperature. Conversely, PDs due to mouth, skin and eyes’ dry were significantly affected by room air temperature (p ¼ 0:015, 0.023 and 0.015, respectively). In addition, most of SBS were insignificantly affected by OTS except that at room temperature of 20 1C, PDs due to nose and eyes’ irritations as well as mouth dry were significantly affected by OTS (po0:001, 0.008 and o0.036, respectively). The results demonstrated that PDs due to SBS were insignificantly affected by thermal gradient. PDs due to nose and eyes’ irritations and mouth, skin and eyes’ dry were significantly affected by room air temperature. PDs due to nose and eyes’ irritations as well as mouth dry were significantly affected by OTS. PDs due to the other SBS were insignificantly affected by room air temperature and OTS.