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, respectively